I run a .45 VP and a piped .61FIRE in Scale warbird racing, both with the 10MM carbs. The VP mod is a little port work and a shot peened crank. Both engines are powerhouses with manners. I will admit that the 10MM carb has it's quirks but after I learned how it wanted to be adjusted both engines run like silk. Two things can happen, the carb richens up at full throttle so you really need to set the needle at full. At first I thought the engine was going lean. The second is that if the low speed needle is set too lean it will have problems transitioning but will idle just fine. Looking into the bottom of the carb with it in the full open position the low needle should be covering about 60% of the opening in the spray bar. The only other things I have done to mine is add a .5mm head shim, run 15% fuel and an Enya #3 plug. Took me a while to get them set up well but well worth the effort. The .45 spins a 9.5X7 APC Pylon and motivates that airplane to about 130 MPH. The .61 spins a 10X10 and motivates it's airplane to about 150 MPH but sadly is still getting beaten by the YS 115's.