ORIGINAL: Hobbsy
Double f, I like to use engines on the lower end of the recommended range, that lets me be a pilot instead of just a throttle jockey. I got heck for this the very first time I flew a plane. I had a Kombat 40 with the 60'' wing option and had an Enya .46 MKII. Everybody who looked at it said it wouldn't fly because the engine was too small. Well, somebody forgot to tell the engine, it flew just fine and it was 100 degree day in about 1991. That was my very first flying lesson.
I think that's exactly why most scale plans designers don't recommend over powering their aircraft. They are supposed to fly in a scale like manner.
The Hughes H1 Racer was a record setter, not because it had enough power to hang on the prop & go vertical, but because it had streamlining inovations as well as big HP. (for it's day)
I doubt that the full sized H1 would have lifted off after a 100 roll & went up @ a 75* angle to 5,000', but it seems that todays modelers want that kind of unrealistic "non-scale" performance.
My 16# 89" PT-19 W/an FA150 on EI/glow fuel wouldn't do that, but neither was it underpowered. It would give somewhat "beyond scale" performance.
Even a 180/200 class 4-stroke would give "beyond scale" performance in a steamlined <18# Hughes H1.