At the moment I have 3dmg/1acc/1endred/1hold on mine and I've no problems while soloing on invincible. (I have Cinders too, with 3rech on it besides the other slots.)
I'll be changing the slots on Char for the hami raid but doing missions they're the slots that work for my playing style. 
I'd go for 2acc/2 rech/2 hold all the way
I'd go with 2Acc/1Hold/3Rech. You don't need your hold to last that long. Fulcrum Shifted imps will get stuff killed in no time, so it's better for you to be able to spam it than making it last.
@False Fiction - Virtue / Defiant
Current projects - [Glaciologist - Ill/Cold Troller] [Cloudshaper - Storm/Dark Def] [Harald Wartooth - Elec/Psi Domi]
I'd go 2 acc 3 hold 1 rech. You have MORE than enough recharge with siphon speed if you stack it, and the 3 holds helps for stacking against EBs AVs, or to last on tough bosses (Illusionists 
)
wow quite a range of replies, I guess everyone slots it according to their play style, I guess I have to experiment for myself.
The question is: when you stack char on a bad guy, does the DOT component stack and does it stack with its containment damage?
@Boerewors
[ QUOTE ]
The question is: when you stack char on a bad guy, does the DOT component stack and does it stack with its containment damage?
[/ QUOTE ]
I believe it does.
@False Fiction - Virtue / Defiant
Current projects - [Glaciologist - Ill/Cold Troller] [Cloudshaper - Storm/Dark Def] [Harald Wartooth - Elec/Psi Domi]
[ QUOTE ]
wow quite a range of replies, I guess everyone slots it according to their play style, I guess I have to experiment for myself.
The question is: when you stack char on a bad guy, does the DOT component stack and does it stack with its containment damage?
[/ QUOTE ]
Yes, you can get it to stack (I have when speed boosted/AM'd), but you'll probably need an external recharge buff, since the DoT is over a 4.2 second period, whereas the base recharge on the power is 8 seconds.
So, with 3 recharge, you'd get 0.2ish seconds of overlapping DoT, but add in hasten and other effects and you can get to to overlap.
Personally, I don't rely on Char to Do damage. I've got 2/2/2 Acc/Hold/Recharge which, while pretty much default slotting works well for me, in that it's likely to hit most things, and if I do miss, then the recharges mean that it's back fairly rapidly to try again, and the duration's enough to stack on a purple boss to get it locked down permanently, barring streaks of misses.
Slot it how you want though. It's not like anyone can see and criticise your slotting ingame 
Warning:
The above post may contain Cynicism, sarcasm and/or pessimism. If you object to the quantities contained, then tough.
2 Acc 2 Hold 2 Rechg until Hami-Os.
CoX 50s: <ill/rad> <ice/ice> <fire/kin> <grav/sonic> <ice/storm> <earth/kin> <kin/elec> <cold/psy> <thugs/dark> <fire/dark> <dark/elec> <night widow> <EM/ninj> <mind/icy>
For a solo fire/kin, what would be the best to slot char?
Would it be 2acc/2dmg/2hold or does the damage not do that much and 2acc/2hold/2rech be better to stack the damage from the hold and its dot?
@Boerewors