My Ultra Stick 40 started life with a Thunder Tiger 46 pro and I should have left that engine on it.
But I got the four stroke bug and after much reading on the forums I became convinced that the Magnum 61 would be the engine of choice.
The Magnum engine ran perfectly but it was barely equivalent to the 46 pro on power. Everyone has their own idea about perfect power but I really don't see how a 50 class four stroke is enough for this plane.
In short order I replaced the Magnum 61 with an OS 70, while this fixed the lack of power the 70 was a lot heavier than the 61. I put a high capacity 6v battery in the rear of the fuselage to balance the plane. It sorta flew like a brick with wings and I never really liked the plane.
I recently sold it to one of my buddies and he put an OS 55AX in it and it seems to be the perfect engine for the plane.
Vertical is very strong, and it floats in for landings now.
When I built mine I set it up for CROW and played with it a few times, then I disabled that programming in the TX, while some people love the feature I would just use the full length ailerons if I was doing it again.