[zoomer260]

I'd put it in and fly. I assume you are not in search of the perfect 3D monster etc. Sachs 4.2's were put in 84 inch planes all the time. I know more than one 90" Comp-Arf with a 3W 75cc in it.

Yes, by todays standards it is a heavy engine for that plane. Back when power seekers would have done it and did. Put the Rudder servos in the tail in a push pull and place the batteries far back near the turtle deck and I'll bet it will balance without any dead weight.

That's really all that matters, can it balance without a bunch of lead under the tailwheel. As far as the plane being rated for that size it's a damaged plane given to ya. No warranty to worry about and throttle management is a nice problem to have.

People are putting 40cc gas engines in 1.20 size (74") planes now. Moki 1.80 and 2.20 in same planes. Something I would not have even considered 15 years ago.