I have two TT Pro.25 that I bought when first trying combat. Put them on two Predators. One did better than the other, but both were dogs compared to the OS FX and Norvel. I bought OS 40 FP carbs from a guy off the web and they were better, but still not competitive with OS/Norvel. Finally bit the bullet and bought 2 Norvel--lots of power, but lots of headaches also. I put a mouse can muffler on one of the TT's and use it on a PBF just to knock around with--it will hover ok, but I don't have quick enough throttle to tail touch. Dang thing keeps flopping over, or laying down. Still a blast to fly, though.

In summary, the TT Pro.25 is not a very competitive engine, even when running well. I have kept one for back up on an Open B rudder plane, but much prefer my Norvels.

Good luck.

Greg