That's a pretty large wing for the desired engine size. I would try to keep the thickness down to 16% or less. I designed a pretty decent 1/2A for an .049 at 201 in2 and 16% and liked it. So if you try to stay to strict scaling from the larger plane, I'd go smaller than 300 in2. If you thin the wing, maybe it'll pull it at 300. Everything else needs to be pretty low drag and low weight, too.

The 1/2A Pathfinder is only 236 in2. The Hunter Stunter is 225 in2. The upsized modern Tercel is 246 in2 but has the advantage of lower drag from a full fuse. The one I saw that was nearly finished had an awful lot of wood in it. Hard to keep the weight down unless you have magical wood, or get really happy with the sanding block.  (I prefer to build thinner, and accurately and not "buy it back" with sandpaper.) If you want to go bigger, then look at the size and weight ranges that Rich Porter achieved with his Ridiculous. That escapade resulted in a 555 in2 plane at 20 oz using a TeeDee milked for all it was worth, including car head heatsink, etc. But he needed a ton of outthrust to get that combination to work for him.  (Model Aviation July 1985, August 1985.)

So it also depends big time on how hard you are going to run your engine. Combat prop and a million rpm? It won't have the disk area so the flying speeds to carry thru maneuvers will likely need to be higher--but it'll pull a larger plane.

The Divot

 All good advice from Larry and Dave above. Without going into a bunch of percentage calculations and assuming you're running a decent powerplant, don't be afraid to use a "real" airfoil with a round L/E and bit of thickness to it. It's 1/2A though, your main goals are to keep it simple and LIGHT. Aerodynamically, stick with eyeball proportions relative to the "big" airplanes. Thin airfoils have typically been the weakest link in many 1/2A designs IMO. Again, and as with all our models but especially 1/2A, keep the weight down as much as possible. Adhere diligently to these guidelines, get your engine running good, make the right choice on lines, and then be amazed at how well a 1/2A model can perform.