You're under propping the engine for sure. For better performance I'd be looking at a 22-8 Menz, 22-8 NX, or a 22-8 or 10 Mejzlik. All of them put the engine in an excellent torque/rpm band.

Oh, yea, tweak the needles. Your engine will have more than enough oomph to performance fly a 19lb. Ultimate if it has any wing area at all.