I know for a fact that Crossfire Coupe's hook up much better with big power, because the R170 is limited to 255 / 35 x 18 rear tyres, I did look at tubbing one, but the rear 1/4 windows mech encroaches so not really feasible.
My V8 R170 needs a definite specific launch technique and a bit of luck on a hot day after a good run to get the rear Tyres hot and sticky and the Roof folded into the Boot above the rear end to get a whole 1 second better times.

I'm pretty sure Crossfire (Coupes at least) can run bigger Tyres

Your comments re the Crossfire Coupe shell being stiffer is extremely valid and something I had never considered

Tuning wise the general consensus appears to be that power outputs are the same, just the claims are different.

Needs a dyno shoot out