I'm working on an outrigger set up for a .40. So I'm debating between O.S. .21 VZ-M and the O.S. .46 VX-M. They are both claiming 2.5 horse. the .46 will make that at 23K RPM and the .21 will make it @ 33K RPM. The .21 has a mass of 12g and the .46 is 15.7g. So I'm thinking that the .46 will have more torque inturn, I can mount a larger prop. Though, the .21 will turn a max of 40,000 RPM so less torque but more horse and a smaller prop? I don't know some one friggin' help me here!