I put an MVVS 40 in a Morris Pen-Knife(calls for a 21 size) This plane was no fun at all because it had so much power and extra weight, It never allowed any relaxation, period. Ran it out of Fuel on approach at about 15 ft....Don't know if I will repair it, if I do the 40 will not be on it. A friend has a Doghouse with an Enya 90 fs on it, flew it the other day, same problem a dead stick will be hairy to say the least.