I recently got my Senior Telemaster ARF. I am also still unsure about power. I initially decided to use an OS FS .91 and tow the occasional glider and drop candy, some night flying also with some kind of nav lighting system. Upon getting and inspecting, the fuselage is way way flimsy.....the preinstalled beam engine mount does not reach back into the framing far enough, to hold much of a larger engine. Looks like this thing may shake apart unless I do my usual ARF-beefing procedure with balsa and epoxy. Seemingly, Hobby Lobby is going for electric conversion in all their products. May be why the Telemaster is so frail....to save the weight for the $500.00 + worth of motor, batteries and speed control. Too expensive for me.
Going for the balsa and epoxy... gotta engineize this thing. That BME ST 91 gasser sounds like something worth looking into.