7.25 diameter prop
Your right. On launch it is barely enough. But with the qm40 engine im stuck. Still not hitting the pipe yet. Going to shave a little more. The 9x10 @15.5 is not much more thrust on launch either. On the 4.5 pound plane its going to be shakey. I saw on another thread someone using a 7x9 prop on a DD. That will not work on a whiplash.