The RCV .90 would be an excellent choice, I have a RCV .90 on a H9 P51, it turns a17x6/10 Zinger four blade at 5,500. Otto sugested a 17x10 or 18x10 would be even better to hold the rpm to 5,000. I tend to agree. I also agree with Sport that the more blades and less effeciency thing is way over rated. At four stroke and Diesel rpm you can't tell the difference.