For the CA 31% plane, you could also use a ZDZ-80 twin. It weighs a little more than the BME-110 (4.1 lbs bare), with less power and cost. On a plane weighing 21 lbs and with low drag, even the 80 twin would be power overkill. The only downside to the 80 twin is it is wider plug to plug than the BME.