20" props OK with 50cc Rotomax, a Suppo 7035/8 or a 50c rimfire?
 

I want to replace my two 2.1 Moki engines with electrics. The mentioned large motors are all designed for 22" to 26" props with 12s lipos. The Suppo can take a 26" prop on 10 cells or 24" on 12s. My planes are an 89" 21.5 lb enlarged AstroHog, and an 86" 21 lb big Bingo. The heavy motors and lipos will balance the tail heavy planes well as there is already over a lb of lead weight in the nose of each plane. The problem is that I only have ground clearance for a 20" prop. The Moki maidened the AstroHog on an 18" prop, and the Bingo on a 20" prop. The experienced pilot flew these planes very level and tame out of respect, but said he enjoyed the Bingo's performance better. But I don't know if he considered one or both planes as underpowered with those props.

I'm new to big electrics, and so my question is if it is too much stress for large motors on 12s to run small 20" props on these planes? Perhaps I can increase the twist from 8 or 10 to a 12 twist for more power?? I just want these heavy planes to do simple rolls and loops, but don't want to burn the motors up either. (if that is even possible because of too much spin with so little resistance, on too small of a prop).