Stick with stock size. My buddy had 555R on his C5Z06. He did one or 2 road course days and I think once at the drag strip. He still managed to get almost 15k miles out of them.
I wouldn't recommend an R comp to any unexperienced driver... especially with stock drivetrain. YOu might be better off looking into a good extreme summer tire.
2003 Corvette Z06 - MGW shifter, Corsa X pipe, Corsa Xtreme exhaust, Texas Speed long tubes w/o cats, PowerStop rotors/pads, Conti DWS tires, C6Z51 F&R sways, C5R headlights, tuned
04 GTO - sold