RE: 8.8lb plane with a .61, how will it fly?
It will take off for sure, the question is what type of flight do you expect ?? straith and level or basic aerobatics such as: loops and slow rolls !!
for that weight a 90 2-s will take you to limited verticals but enough for stall turns, imelmans at take off and good knife edge, as well as, all "traditionals" piruets.
If you wish for more check your 4 strokes options YS 90 or 110; OS 120 etc.