As a reference point of questionable validity, from a piped OPS "Speed" .15 (which is actually timed for peak hp in the 23-24k-ish range, not really "speed") when I bench ran it for pipe tuning on a 90% diameter version of a 6x5.5 prop, I saw 24k. So in the air on the full prop I would expect to see about that. This is a good example of a .15 that weighs the same as a .25.. it's chunky as well. Maybe it has its roots in a car engine.
http://www.youtube.com/watch?v=cH0OA5-VVgY
I looked at those NR .12's and .15's recently but when I saw the weight I recoiled.