I've wondered about a glow conversion this one and/or their mini-Funtana. The wing area is large enough it seems a .30 4-stroke weighing about 10.5 ounces might work----just a few more ounces than electric spread over that larger wing. I have to fly off grass so I don't think TO and landings would work well enough.

RC Report tested the O.S. 15CV-A as putting out 35 ounces of thrust using a 8x4 prop and 37 ounces with a 9x4 (11M RPM). Since the mini SHowtime weighs 26-29 ounces per their cataloq you might be somewhat lacking for 3D power. The .15 would certainly fly it aerobatically though. That is why I was considering the .30 4 stroke although at more of a weight penalty.