Old F1s at the track

[jwg2]

I'm about to retire a set of old F1 Supercars from my 2001 Z06. They have some tread left, but not much. Thinking of hanging on to them for use and abuse at track days (at least until they are shot). One of the reasons they are worn is is from track use, and I found them to be decent compared to some of the other street tires I've run. Going forward though, would a set of nice evenly worn F1s be good or bad for the track performance? How does a worn tire compare to a new shaved tire of similar tread depth? My other thought is to spring for a set of new Hoosiers. What size Hoosiers would I need for a 2001 Z06? What do they normally run? What are other good options for a road racing tire? Obviously, I wouldn't run them past the point of safety. I'm looking for education on tire performance.