I have a MDS .58 in mine and it has unlimited vertical and will hover at about 2/3 throttle. My MDS spins an APC 13X4 at 10,400 RPM and is actually running very well!? I also used a very light Brisson pitts style muffler, 2 ounces less than the stock muffler and a Goldberg nylon engine mount instead of the heavy, breakable, metal mount. Even then I had to put my 1500 mah battery pack as far back in the tail as I could and add an ounce of lead by the tailwheel to get a 4 inches back from the LE CG.

I now have 10 flights on my US 40 and it is the funnest airplane I have. I love the crow mode! It's pretty cool to come screaming down the runway at full throttle with crow mode active, pull back the throttle, and watch the airplane stop and gently settle in for a perfect landing!

My only complaint is I cannot get mine to knife edge. And I too had the supplied fuel tank split and fill my airplane with fuel.

I think the US 40 is just about the best $130.00 model out there!

Cheers!

Galen