Hi,

You need to give us a little more info for us to help a little. What is the wing area and wing loading at 120 lbs? Wing airfoil type? Flaps? slotted flaps? What percent of chord?

a 9ft wing with a 1.5 ft chord = wing loading of 145 oz per sq ft of wing. Very heavy loading! with a 2.5 ft chord, the wing loading drops to 85 oz/sq ft wing. Still very heavy!

How slick is the airframe? What flight time are you shooting for? What is your max fuel load possible?

I would think that you would need to be able to fly the plane at partial throttle at 500 ft agl before your power ratio is high enough to fly at 20,000 ft agl even with remote tuning.

Elson