I built a Sig Hog Bibe about 20 years ago. It was a great flying plane. You are way under powered with the OS 91 if you want to do a maneuver such as a hover. Full throttle just to barely hold the plane vertical is not adequate. You have to have enough power so that if necessary you can add throttle and fly upward out of the hover. In other words you have to have more thrust than the plane weighs. For example, if the plane weighs 7 pounds you need an engine that would give 10 pounds or more in thrust. If you are at full power just to hold the plane in a vertical attitude and you lose control, you have no option other than to fall off into a decent to gain flying speed. You try to hover too close to the ground and that happens, you will crash before you get enough flying speed to recover. I would want twice as much thrust as the plane weighs which in the example given would be an engine with about 14 pounds of thrust. Hovering requires a series of revving up the engine while in a vertical attitude so you have to have plenty of thrust to do that.
One thing that would help is to have a prop with low pitch. You would probably want a 15 x 5 over a 14 x 6. It's sort of like being in first gear in a car. You get maximum thrust but not much top end speed. Of course the prop must be within the working range for a given engine. The lower the pitch, the better for a 3D type maneuver. As you go down in pitch you usually have to compensate by going to a bigger diameter prop. In doing so, you have to consider that the larger diameter prop will give less ground clearance. That needs to be considered.
The Hog Bibe is a fine sport plane but not really designed for 3D maneuvers. Most 3D planes will have huge control surfaces compared to non 3D planes. With large control surfaces you need to keep overall speed down to lessen the problem of flutter. As you can see, there are are lot of things to consider and I've only touched on them without great detail. Enjoy the bibe for what it is and if you want to learn to fly 3D then get a plane designed for that purpose.
Mike