I've been flying the H9 Sukhoi with a GT-80 for about 4 months now. The engine is still getting stronger. It turns a Bolly 24x10 at 7450 RPM and a Menz 24x10 right at 7100 RPM. The Menz definately flies this plane with much more authority and has better hovering characteristics. Up line maneuvers are also much improved with the Menz over the Bolly. Down line braking is about the same. Originally, I ran the stock mufflers with the baffles drilled out like the Sukhoi instructions mention doing. Now, I'm running the Slimline mufflers with smoke inserts and think the motor is a bit stronger than with the drilled out stock mufflers. Hope this helps and gives you a bit more data.