My Stock (70t) car is a 90MM RM and I have a 991 GT3 body as well, I am running 0N on a wide front of end and 0W on the rear. I also find it quick but a wee bit off the pace of the GT1.
Cheers,
Jim
Jim, what's the setup on you 90mm car? Both my box stock 90mm cars bounce a lot. I'm running PN super soft blue springs in front and relatively soft t-plates in rear.