Elganja come on out with us for the BMW NCC event or the PCA Potomac and we’d be happy share a few pointers. 21s are very doable with some decent rubber and loads of commitment.
My car is setup with the BW GTmore suspension, half cage and race seats, and got it into the 19s on some Michelin takeoff rubber.
https://youtu.be/PdJ4ZcDQpkM
Peter