Thanks for the info everyone , but novabill's advice is what I wanted to hear. I ran into a guy in a LHS once and he began explaining why he was buying a 13x what ever prop. It turned out he wanted to hover a regular plane , something not 3D, and was instructed to use that prop for his engine. So I will give it a go this week end with the 13x6 prop which I have already for a SU-31 .60 project I have going .