A P-60 should be fine. Terry Nitsch used used to fly a BVM P-80 with a JPX propane powered turbine that only put out 11lbs of thrust. A modern engine install will be much lighter and the P-60 puts out two more pounds of thrust. I think people tend to over power some of these older designs, that were, after all, designed to fly with a ducted fan that produced about 13 lbs of thrust that decreaed progressivly as speed increased. A 13 lbs thrust turbine makes the same thrust throughout the speed range.