Yeah and I don't like slipping the clutch either, gotta drop the tranny a lot more often to replace the disk and fix the hot spots, but that's what most people do. And of course slipping it means there is less stress on the tranny internals, especially running cheaters or slicks...
As far as the geometry, you can change every aspect of a Supra's suspension because it's designed to be an awesome GT class racecar. So since it's independant rear suspension you want to make sure that when it squats off the launch the toe and camber and all that jazz are letting the tires remain in the best contact with the pavement. That is why the fastest Supras (Paisley, Vin10) are running true drag-style non-independant back-half rears like the old-school muscle-cars. So they're always getting the best tire contact.
You can have an 800 hp Supra that you can't get to run 11s because the suspension setup is shit, and I know of a guy out there who's been palgued with that exact problem.