My 20s with tires actually ended up weighing 1 pound less than the stock wheel and tire.

 

I second the spares in the front and sticky mickey's in the rear. Best combo possible

 

I share your traction issues with a S/C. The best that I've done on street tires (my 17" 235 P-zeros) was 1.95. Even so, nothing touched me that did not come in on a trailer at the local test-n-tune night. I'm not sure what type of supercharger that you have, but watch the launch RPMS. I could leave at a whopping 1500 on the 235s, but now I'm up to about 2500 and a feathered clutch with 275 street tires on. This is my work car, so I don't intend to put slicks on...somethings gonna give...I'd rather it be the tires!! I saw two broken axles (one on a Mustang) last time I went racing.

Good luck spanking the bow ties. I had a STI/WRX or whatever that Screw-be-u with 16lbs boost licking his wounds last time I went to the test-n-tune.

 

Our spare tires are embossed on the sidewall with a max speed of 60mph (+/-). If a track's tech inspector is on his toes, he will not pass a car with spares on the front. Just air up your regular tires a few psi below the max shown on their sidewall.