RE: SJ 50 vs Cast Q500 AAC
Terry, I've had my SJ.50 on a Predator in the past and it was no where near as fast as a BSE SS Q500 motor. I use it in my Magnum which is a pretty slick plane too and only get around 160+ with it.
If you go back and look up the Carolina Speed Rally you can see data from different engines and airframes.