As I have said many times on RCU, I use the 3W-24 as the main engine in my university research project on aerial sampling. I have 15 of them and each one will turn a 18 x 8 at 8000 rpms. The best prop for the sport flyer is an 18 x 10 because max rpms of 7400 is at the peak of the torque curve. I tested the RCS 140 and its performance was not even close plus it is a very fragile engine.

A good running 3w-24 will take a 12+ lb plane vertical and unlimited.

Elson