Help with Wheel and tire combo please!

I run 295/50-15s at the back,under my FormulaS. I find the BFGs only have traction for about 25% of their tread life. The Cobras seem to last a bit longer. When they stop screaming, theyre done.After that they get hard and seem to last forever,though. I take em off and put em on something else. Or burn em up. The 295s help keep the back, in the back, around turns, when sliding under power. With 275s I kept spinning out.
I too prefer the looks of 50 series tires, or maybe 45 at the shortest.