I have been flying 2 strokes on my 3D profiles and have not tried any four strokes yet. However, I have compared the Irvine .53 to the Jett .76L that Bob mentioned above. I can say that the difference is in the prop... The Jett can spool up a 14x4 without any problem. The Irvine .53 and other similar .46 to .50 2 Strokes typically spin a 12x4 at higher RPM. They get the job done just fine, but the vertical is noticeably sluggish compared to the Jett .76L. To me, 36% more disk area (with no weight penalty) is a real advantage for 3D.

TX