So you're saying you get a light clutch pedal after doing launches at 6,000 rpm?!
Yeah you are over heating the clutch. Not only is it hard on the clutch and shortening it's life, I don't know how you're not getting a crap load of wheel hop unless of course you're slipping the clutch like crazy. If you need to launch the car try about half the rpm you're currently using. I do multiple launches when I autocross and this has worked well for me with minimal overheating of the clutch.