I have a TT pro 46 spinning a 12.25X3.75 APC prop on a 3D plane. When I do an upright loop it runs fine. If I do an outside loop when the plane reaches the top of the loop it looses all power and almost cuts off. When I finish the loop the engine speeds right back up. Also if I am attempting a waterfall or blender it will lose a little power in the process but not near as much as it does in an inverted loop.

Engine has about a half a gallon through it.