DPViper,
Siping is very common on off road or all terrain tires. The tires on my Jeep and F-250 are "siped" and have great traction in the wet, mud, snow, etc. These tires are not speed rated, however.
I would follow SnakeEye's and others advice. Don't cut your tires. I have major traction issues too. I am planning to buy a new set of rims and tires very soon, but would like to stick with stock sizes. (Paxton install, car back next week).
I believe, now that the Corvette has 19 inch rears, we will get a better selection of 19 inch tires. I will likely do as Kai is doing and get a set of tires for the track / street, probably PS2's when they become available in 19 inch sizes and a set of DOT approved slicks in 19's.
FYI, I have read that the regular pilot sports (non-run flats) offer a considerable improvement in ride and traction. Also, some of the track guys like the Kumhos. Sadly, they are not yet available in 19 inches either.
Question for the group, does anyone have experience with both Pilot Sports (non run flats) and PS2's? I wonder how they compare.
Good luck,
Dan