RE: Bigger engine for U-Can-Do .46?
If you have the $, get a YS 63 or whatever they have in that size now. plenty of pull and light. The OS 55 will also work with noticable improvement.
If you plan on changing aircraft soon, keep the motor choice flexible to work for both.
4 strokes are mostly preferred as the power curve is very ideal. Please omit HP postings, they do not represent real usable power during flight.