I have a similar setup with a 50 TCCD (similar kit) and had what sounds like the exact same problem. Clutch tuning is definitely the secret to fixing the problem. I had a two shoe with Paz springs tightened as far as they could go and it still would not engage high enough once the motor got warm. I was able to fix the problem by taking a bit of weight off the shoes. Now I have great power all around (and that is with 16x45 gears).