I have ran an os .25 for a few races and it is a very nice engine. If you have a good smooth throttle finger it is possible to pit at 10 mins too, I usually pit at 8 just to be ont he safe side but the OS 25 is a nice inbetween the 21 and 28's. Price isnt too bad either. But my all time fav in the truggy is the OS speed, lots of power, great runtime and perfect balance. the Nova P5 runs great in a truggy too.