Hi Dan, a friend of mine has one of these and we've used it for a lot of flying (CL). They are really nice little engines and highly thought-of. I don't have any other engines of that size (or a TD 020), so I can't really say how it compares power-wise. My guess is that it's pretty good, though, and your idea of a TD 020-size model would be fine. Maybe something a bit bigger, even. Expect to use a bigger prop than the TD would - something around a 6x4 seems about right for CL.
My friend had his in a slightly enlarged Stunt Chimp. It was quite capable, and surprised a few people. I can try and find out the dimensions, if it helps. They're a nice engine to use, and not fussy with settings. Just beware flooding it - you don't really want more than about 1 choked turn, plus maybe a touch of fuel against the closed piston.
Steve