As Budd said, you’ll find you haven’t approached the limits. At 200 pounds you’ll tax the GS500F’s suspension on the track, but that is a good thing. Get some aftermarket fork springs and bump up the rear preload before hitting the track. You’ll become a better rider starting your track days on the GS500F instead of a GSXR 750.
I agree comfort is subjective, but I cannot fathom someone who is 6’2″ being more comfortable on a race bike than on a street-oriented sport bike or standard motorcycle. I can imagine your GS500F getting uncomfortable after two hours. Easy fix, there. Stop and take a break. If the F’s riding position makes you uncomfortable what makes you think being folded into a racing crouch will be more comfortable?
Sounds to me like you’re taking a mature approach to this upgrade process, but there is more to safety than just maturity. You need to learn how to stop properly and practice the technique until it becomes a reflex. Same for cornering. When, not if, you get into a turn a bit hot and spot a hazard on your cornering line you need to take the correct action instantly. You won’t have time to think about it. Your GS500F has a bigger margin for error than a race bike. You may very well develop the skills to go directly from the GS500F to a GSXR 750, but you need to develop those skills on the slower bike. As I mentioned above, you and the track instructors will know when you are ready.