I'm afraid you're going to find the .15 is WAY too much for the mini Telemaster. A friend of mine tried a .15 in a Herr Cub, which is probably a heavier airframe, and found the engine torque made it uncontrolable above 1/2 throttle. I'd stick to something like a .061 or maybe a .074 Norvel as a maximum for this plane. I have one myself I plan to use an .049 norvel in.