Advice - optimal tyre width for track

[Ski1]

Hello all.
I'm sizing up some track rims and tyres. I'm aiming for as light as possible, but with the right amount of grip.
I'm not chasing the widest, heaviest setup. Quite the opposite.
So for those of you that track regularly, can you let us know your power setup (tune etc) - what width tyres you are using and if you think your width/traction is enough, too little etc. Subjective opinion and feel is fine.

Yes - there are different tyre options, and a change from 18 to 19 or vice versa etc etc will have an effect. This thread is not about Yoko vs Nitto, etc - so please do your best to not bring that out. To put it another way - given the tyres you have and the width you have do you feel you have the right grip, or could you have gone lighter (not as wide) and still retained ideal traction?

My spec:
E92 M3 with BPM Stage 2 hi flow cats and M3 world full exhaust system. About 330kw at the engine.
18 inch rims

Note: Improved production E92 with 500hp - runs 255/18 square full slick. Clearly very light car and light wheels/tyres - and for that setup there is enough traction with 255!

Your views appreciated.