I've had a ST G75 and currently an MDS .68 on my MkII version. I can pull mine vertical for quite a ways before it sags, but what's the point? It's a not a hotdog kinda plane. I love mine for relaxed Sunday fart around the sky.

Anything .60 and up 2stroke will fly this plane just fine. You can hang up to a .91 2stroke or 4stroke no problem. Any larger, and you'll need taller gears to clear the prop and lead in the *** to balance.