I am flying the knew dp extra with a moki 1.8 at 4200ft elev. right now I am runing an APC 18 / 8 . IT does not seem to pull like it should.. I just orderd an 18 /8 BAMBULA will this help. What would be the right prop for this elev 19 /8 20/8 or more pitch

20/8 is too much for this engine. It will turn a Mejzlik 19/8 though. I am running a Zinger 18x6-10 and am happy with the performance. Your altitude will seriously hamper performance no matter what prop you are using.

I think that a moki should hover 14 lbs plane at 4200ft. I cant belive that i would lose half my power it should put out at lest 16 lbs of thrust at my elevation.