So here are my thoughts on this one. Instead of putting a heavy gas engine in it, just do an OS 160FX with a Slimline Pitts muffler. Keep the weight down and it should be a great IMAC flyer. I have no intention to do all out 3D with it. Single Fromeco 2400 maH Relion and Hitec 5985's on the control surfaces.

On another note, you could also do a tuned pipe. Does anyone know anything about tuned pipes on an OS 160?