Double clutching is the answer to awesome downshifts, it rev matches and takes off without the tell tale bouncing of normal downshifts. I have a WS6 Formula M6 also and I've done a 6-2 double clutch downshift. On the WS6 first it good till 50, second till 75, third till 95, fourth till about 120-125 so technically the only one I can't do is a 6-1. Granted the WS6 has 3.23 gears as opposed to the GTO's 3.46 but the GTO has a 6500 redline rather than a 6000. Hell I hit almost 140 in fourth in the GTO. But practice double clutching downshifts, you'll love it when you get it right and it's safer than just normal downshifts.