Prop selection also goes a long way in maximizing your power/weight ratio.

Remember that a staud is a very shortly coupled plane, and arent really designed for 3d work. The staud in general is similar to a giles 202 in its flight envelope. There are several GP Ucando's runnin saito 100's, around 7 1/2- 8 1/2 lbs, and they rocket out of hovers, accellerate vertically, etc. They are also doing it with 16/4 props. That staud isnt going to like to fly that slow.

Do a search on the saito 100, and see all the various pros/cons of the engine, and how many planes they are run in. You might also be able to get away with lower nitro% in the saito. Another thing to consider with the YS is the fuel tank, the pressure system seems to like to split stock tanks on quite a few planes.

Just some other things to consider.

Steve