There are a lot of car style .12's that are quite powerful as compared to what the airplane styles have on offer. Just the crankshafts are short, and the heads need to be trimmed. They seem to weigh about the same as a .15 too, which gives them a lot of negatives. They put out power like a good .15 though to be on the plus side. I don't mind weight if the power is there. As far as a heavy plane is concerned, a good solid mount is prefereable to anything flimsy, as the motor runs better. I don't think bearings would notice anything. We made solid motor mount crutches out of heavy aluminum castings, and the planes were quite heavy, using bass for wings, fuselages and tail surfaces. They really did not slow anything down. The proto (standing start) planes needed to be lighter though. An RC one is changing direction a lot, so weight is an issue, but I would still take power over a bit of weight-if you want to go fast. Picco and Novarossi come to mind for good .12 size motors. Fora makes a nice light .15, as well as some other F2D combat designs. They really shave the weight and put out power. No throttles. CP has used them with success for RC. I think the AP .09 rod bushing is left off for a reason. The piston is lighter than the .15, and there is less stress. I would keep the revs down to the low 20s, myself, as it is really a sport motor.