I think a 91 will be overkill. It is only a 30-40 size 2 stroke, and looks like it sits pretty low on the front, so you might are going to have prop clearance problems. The nose weight with the 91 might also be a problem. IMO at 5.5 lbs a Saito 72 will be a great combo for this bird. Just my $0.02 since I don't own one and am just looking at the specs.