Its not so much a firm 1000 sq. in. area, as it is the wing loading for the particular airframe. If you are not pushing your luck on wing loading, you'll be fine. Your example is pretty close to a Carl Goldberg Extra 300 at 852 sq. in., which flies great at 9.5 lbs or less. So there is a sample weight vs wing area (or wing loading) to shoot for. If your conversion engine will put your plane well over this weight, it's a crap shoot. The engine will pull the weight around no problem, the airframe just might hate you for it, and let you know all about it during stalls, and landings I personally enjoy test flying overpowered, overweight planes for their size....but they really never fly GOOD, ya know? Sometimes you get lucky with larger warbirds that can literally weigh 20 or 28 lbs and still fly great either way. But smaller aerobatic models usually are not so forgiving.

Chad