[gtc]

It would help to know exactly how he modified your SC calipers, and what kind of rotors he installed.
It sounds to me like he is wasting your money.

If you're looking for cost effective brakes for the track, the best thing to do (IMO) would be to have your SC calipers rebuilt by PMB or some other competent party, and invest in a brake cooling setup.
There are more brake threads on here than you can count... read a few threads with Bill Verburg or KTLs brake comments and you should have a better idea of what works and what the worthwhile upgrades are.