If your ASP XLS .52 turns that APC 12-4 at about 14000 or so it should rocket skywards a plane of 2500 grams (I think your engine is strong as you say that you are afraid to overrev it on a 12-4, which is impossible by the way) I really don`t understand the problem here, is the air thinner at your location or something???? since you don`t get the same pull as everyone else when turning a given prop at a given rpm???


If you turn the 12-4 in the high 13K`s approaching 14K and your plane is 2.5 kilos then you should be able to go vertical forever.

Bottom line is: Loose that 11-7 and use the 12-4 APC or 12.25-3.75 APC if you want thrust. That engine loves to rev and can tolerate ALOT more than these props. I have flow on a 9-6 turning over 18000 rpm static and the engine loves it.


Edit: I just noticed that you only use Master Airscrew props, but still the Master Airscrew 12-4 should turn up high rpm`s and pull like a mule. Let the engine rev