Not in a position to comment on that rubyred since I still haven't flown mine (don't ask) but Dick Pettit used an 18/6 wood zinger at 1200 low end and 7500 rpm top end I think. I do know when we looped a real one we nosed it over first to get up a little speed going into the loop so if you're applying down elevator in that sense it should loop with no problem? What fuel are you using? I've always used 15% and seems to be ideal for me.