OK guys report from this morning. to recap: stock ARF, sig tail wheel, 2 elevator servos, pilot , battery on back of motor mount, OS .91FX 2 stroke, slimline pitts muffler, stock spinner, no lead!

7lb 9 oz
CG at -5 inches from leading edge of top wing

15/8 prop; clearence ok but cut grass, could barely idol low enough to keep plane from moving on ground, flew well with great verticle, little fast at back throttle sweet spot.
14/6 prop; did not cut grass too much, idled well without pulling plane, flew well great verticle but seemed little less than 15/8, still fast at full throttle but slows nicley at the back throttle sweat spot, more scale speed seemed like to me.

I will try 13/8 in the morning. This prop is supposed to maximise horse power of the motor and run at the highest rpm of recommended props 11,500. 2000 rpm over the 15/8

the rated rpm of my motor is like 15000 rpm and no recommended props over 11500rpm whats the true horse power....who knows