If you are a fly-on-the-wing kinda flyer, .60 2stroke should service the 'Lady fine. Around when I started RC, I'd seen many an Astro Hog flew with older non-Schnerle .60 engines. The hog has about the same wing area, and many of them were silk, doped, and painted to around 9-10lbs.

These days, however, people consider an airplane underpowered if it can't pull out of hover with authority. I can't argue with the never-ending lust for more power, as I am guilty of it too sometimes. And if there is a better ship to overpower, the 'Lady is it! Those long legs just beg for a big long wood... prop, that is. Looks like an 18" prop would clear no problem.

Personally, I would strap on an 1.08 2stroke or 1.20 4stroke and take her to town.