[kyriian]

Plenty of track groups would permit running a convertible without a rollbar, basically, once you sign the wavier you really are on your own.

For running my Z4MR on the track, I am leaving everything stock, and just use like CG locks or the old autocross trick to lock myself in place. Stock works and is tested, either you have a custom rollbar made, mount a proper 5-6 point harness and a proper FIA race seat in the car, or leave it stock. Personally safety is a do none or do them all sorta deal.

DS2500 is a dual purpose pad, a good dual purpose pad, but still not a proper track pads. Just remember, the more capable the brake pads are, the faster the pad eat rotors, and the more corrosive and dusty brake dust comes out.