You asked about gassers, Mark JR. Gas vs. glow is a whole different conversation. It sounded like you were settled on a gas engine for this plane, but if not that definitely opens up your possibilities. IMHO, a draggy plane like a Cub flies best with a 4 stroke because of the larger props they can turn. And since it's a scale plane, the 4 stroke sounds right too. A Saito .91 would be great for your plane.

On a Cub, there is a lot of leeway. It's not like you are racing or doing aerobatics and need to get every little bit out of your combo. You're just going to putt around the sky in a big yellow plane. A strong .glow 60 will fly it well on smaller props turning more RPM. The .65 LA won't. Any .90 2 stroke will have more than enough power, We've already discussed gassers and 4 strokes, so there isn't much else to say on that topic. The fact is it doesn't really matter as long as you stay in the range we're talking about..