HP,RPM,Torque-doesnt mean much to me, its thrust/weight thats all important for 3-D, hovering most. If you can get real finished weight numbers, then all you need to know is thrust of the engine, in general you need at least one size up from recommended engine.
If I built a .40 size I used a .50-.60 engine, 60 sizeusually a .90 and if .90 sizea 1.20 engine. Nirvana starts at 1.5:1 & higher,then hovers are better and less work for the engine. For some reason, 30% gas planes and larger(the best of them anyway)work well with the recommended engine if you stay with the top choices. I get great thrust/weight with all my 30% gassers & DA50's. When I was flying only glow, had a harder time getting the best combo, always wanting more "thrust". The best glow engine/plane combo I ever had for hovering was .90 Fusion/OS 1.20AX-plane weight was around 7 lbs, engine thrust was probably 13lbs or more-hovers were getting 5 minutes long, almost boring!!! I even had a few 1.60glow/40cc gas planes, this size is not where its at IMO, gas engine too heavy, glow not enough power, sucks too much fuel!!!