Afaik, Kheldian resistance cap is 75% (or is it 80%?). Light form is around 50% unenhanced, so with 3 SO enhancers you'd reach the cap.
Unslotted, and with no slots in shields either, you'd be close to the cap as well (I think they are at around 20-25% base resistance)
Icelock - Ice/Storm Controller
Command Bot 1 - Bot/Traps MM
Kheldian resistance cap in all forms is 85% 
@Double
Double Flame 50 fire/devices
Double Shade 50 tri-form warshade
Double Light 50 dwarf-human peacebringer
Double Control 50 earth/rad
OK, i'm reposting as this is an importent post and I'd like everyone to see.
So, after looking in the US board for about 30 mins, i've got this:
Light Form
---------
Running for 2 minutes,
Base recharge time is 400 (6 and a half minutes, maybe more)
3 recharge reduction on LF will give you a recharge time of 190 - 3 minutes and 10 seconds.
perma Hasten will reduce the 400 to 235 (close to 4 minutes).
perma Hasten will reduce the 190 to ABOUT 143 seconds.
So, if you run LF with 3 recharge reduction AND hasten, you get a downtime of about 60 seconds or less, which is good enough.
Now, the interesting part: Resistance.
As i've posted above, resistance cap for kheldian is 85%.
I also discovered that Light Form's base resistance (no enhancments) will give you 52.5% resistance to everything BUT psionic. This is excelent.
CLICK ME! - .zip file containing a .doc, download from geocities
This file presents how much resistance everything gives you with 3 resistance enhancments, and how much all the shields WITH and WITHOUT Light Form.
Please note that Incandescence is a 'Auto Self' so is always on.
Please note that All shields = 3 (+2) Resistance Enhancements as a level 50 will have.
So, after downloading the document, We can infere that:
Base resistance for the Light Form is 52.5%.
Resistance with all the shields 3 slotted with +2 SOs without Light Form will give you 44.82% to L/S/C/F, and 64.93% to E/N.
Resistance with all the shields 3 slotted with +2 SOs with Light Form, no slots, will give you 97.32% to L/S/C/F/T, and 117.43%. This is a really ABOVE the 85% resistance we get, and so Light Form with no slots and full shields will give you above the maximum, and defending you from some resistance debuffs. I recommend this option as this will also allow you to run with the shields pretty resistent when Light Form is out. If, however, you are running thermal with just one resistance ehnamcement, then an additional resistance enhancment to Light Form (total of 1) is recommended to be above resistance cap AND running the thermal shield itself, but is not a must, as there aren't enough Cold/Fire villains.
Also, if you just want to run Light Form with 3 slots, and without the other shields, this will give you 87.15% to L/S/C/F/T and 107.26% to E/N. This setting will allow you to run around with resistance capped, and if you are debuffed, it will go down from the maximum.
PLEASE NOTE: 52.5% Base Resistance for the Light Form is NOT CONFIRMED.
Thanks to: US Boards, CoH Planner 1.5v by Joe Chott, which I modified to show me the resistance with Light Form (toggle).
As for myself, I'll re-build my build to have everything maxed out, with just thermal shield with one, default enhancment and Light Form with one resistance spare from thermal shield. Also, don't forget Dwarf can resist C/F
@Double
Double Flame 50 fire/devices
Double Shade 50 tri-form warshade
Double Light 50 dwarf-human peacebringer
Double Control 50 earth/rad
Cheers mate absolute legend - can i grab an autograph 
thePhilosopher Martial Arts/Regen/Fire Scrapper
theRegulator Empathy/Energy/Soul Defender
Total Inertia Ice Blast/Kinetics/Psy Corruptor
Total Inferno Ice Blast/Thermal/Leviathan Corruptor
i think those numbers are pre i5/6, the lastest CoH/CoV builder gives them at about 35% for S/M/C/F and 50% for E/NE (that incandesance and qunatum shelid) so those number seem really high, wich puts thne pre i5 to me.
That post is DEFFO pre I5, the res cap for kheldians after I5 is 70% in human form and 75% in Dwarf, if i recall the patch notes correctly and the cap was 85% in all form in I4....
Not to mention that now the base recharge for Light Form is 1000 sec, a bit more than the 400sec on that post.. :\
Anyway, if the cap is 70%(as i'm sure it is) you can slot this with 2 dmg resistance to have it at 75% odd dmg resistance to anything, having your resistances capped with this power alone.
then I have made a mistake, its just that I found nothing new about this.
Also, another resistance enhancment to Light Form, a total of 1 SOs, will be enough to reach the cap and pass it will all the shields. in additon, the maximum resistance without toggles is about 60%, so i recommend putting just one resistance enhancment and running all the shields (endurance is recovering faster with Light Form on).
Terribly sorry for the mistake i've made, but the post above can't be editted by me as the time as pasted.
@Double
Double Flame 50 fire/devices
Double Shade 50 tri-form warshade
Double Light 50 dwarf-human peacebringer
Double Control 50 earth/rad
Off topic question i know but is light forma toggle or click?
Only just started playing my p/b again which is at lvl 33 and was planning on taking light form at 38.
a click, recharge time 1000, duration 120.
@Double
Double Flame 50 fire/devices
Double Shade 50 tri-form warshade
Double Light 50 dwarf-human peacebringer
Double Control 50 earth/rad
I was going to reply to this yesterday but stupidly did my testing in a PVP zone where there were probably other bonuses affecting the results. 
Anyway, I tested again this morning to check what I thought was right (not played much recently and didn't trust my memory). The resistance cap in Dwarf is still 85% - tested by chewing a load of sturdies. I assume it's 85% in human as well.
Dwarf has 37.5% base resistance. Shields are 22.5% base. Not sure about incandecence, couldn't be bothered to find an energy mob to test against. Used to be 13.5%, guessing about 11% now.
So with 3 slots (and Incandecence with the default one slot), S/L/C/F res is about 36% and E/NE is about 49%. Dwarf 3 slotted is about 60%. The figures for light form are correct as far as I know (don't have it to test).
Can't find the Patch notes for I5 anywhere, but i'm pretty sure they decreased the dmg res for human form at least, I may blame all the alchol for this wrong memories 
I think you're right... but I though kheldian human forms got dropped to 75% rather than 70%... could be wrong tho.
Just to have a minor rant, I hate that the combo if I5 and I6 now means it's impossible to get a dwarf form to it's res cap through slotting!
find me: @Ebon Hawk or @Jayd Dragon on Union
Unless I'm calculating it all wrong, human form is still 85% too.
was sort of the point if i5 and i6, or dident you know that ?
I always thought it was 85% cap on all forms, 5% lower than the tank.
Res Cap?? - us forum
IIRC, didn't they just decrease power effectiviness in I5, keeping RES caps the same?
[ QUOTE ]
IIRC, didn't they just decrease power effectiviness in I5, keeping RES caps the same?
[/ QUOTE ]
That was my impression. The idea wasn't to make it impossible for people to have godlike defenses, but to prevent them from having them easily/solo.
The idea was to make buffs always very welcome, and to make it so that a high level tanker doesn't make all other forms of support unnecessary.
A single high-level tanker with a defender sidekick can be very very tough still.
[ QUOTE ]
A single high-level tanker with a defender sidekick can be very very tough still.
[/ QUOTE ]
Not just tanks... At level 37, last Tuesday, I was tanking a level 41 Terra (Devoured AV) in dwarf form, with the support of an empath. I was never in any danger Without the empath I'd have been toast, but she kept me alive so I could hold Terra's attention whilst the scrappers and blasters did their business!
Still, do we actually HAVE any confirmed numbers? Just taken light form last night so knowing how best to slot it would be handy...
@FloatingFatMan
Do not go gentle into that good night.
Rage, rage against the dying of the light.
Light form is 52.5%. The other numbers are mentioned above.
After hitting lvl 38 with Lord Phil I got lightform
but I've heard about resistance caps and slots are so valuable to a kheldian I was wondering how many damage resistance slots in each shield would reach the cap if I have 3 dam res in lf. Im also intrested in how many dam res enhances required in lf if all shields are 3 slotted dam res. Cheers
thePhilosopher Martial Arts/Regen/Fire Scrapper
theRegulator Empathy/Energy/Soul Defender
Total Inertia Ice Blast/Kinetics/Psy Corruptor
Total Inferno Ice Blast/Thermal/Leviathan Corruptor