two extra servos on the airframe. it would be easier if you could mount 1 motor in line with the other (one pushing, one pulling) then you could accompish this with only one servo, of cours, this rules out most models... You would of course need two speed controls. The great planes vpitch system includes blades that end up being 10 inches tip to tip, once installed. The blades themselves are about 4 1/4 inches.