Barry,
When you say the GT30 setup was the best, what do you mean exactly? Better times at the track or better driveability?
If it's the latter then I guess it's just a case of deciding where your priorities are and building the car accordingly. That said if this is indeed a slipping clutch, then given all the money you have spent on this car already, wouldn't it be worth just putting in something that is going to hold the power?
If the clutch was holding do you still think it would return worse results than the GT30 and TP51SPL setups?
Paul