With a 6 foot wingspan limit a low aspect ratio sounds very tempting at first. But beware of the tip votices causing so much drag that you don't get the full benifit of the area not to mention that you can easily wind up with so much drag that the poor engine can't pull the model up to the expected speed.

Seems to me like winglets might just be in style this year...... hint, hint. Or did they short circuit that by specifying a limit on winglets?

If they are allowed I see a wing with a constant chord of about 14 to 15 inches with 14 inch tall winglets having a base chord of about 11 or 12 inches. The spill loading around the tips at the full weight will be quite strong so you'll probably have a lot of incidence at the base of the winglet with a very strong twist to the upper tip. You'd have to do the angle of attack for the wing and set up the root of the winglets with that much "toe-in". Meanwhile the upper tips would be "toe'd-out" to achieve the zero Cl angle of attack. Probably about a 7 or 8 degree twist at least. It would look like you had prop blades on your wingtips ........

The details of the winglets are a little fuzzy now as I read some articles about 15 or 20 years ago but the above is the general idea as I remember it. I think it was Herk Stokley that did a 2 meter glider with a large chord and large winglets to get around the 2 meter span limit without getting into the inefficiencies of very low aspect ratios. It worked very well for him and a couple of others that bult it and reported in the magazines at the time.

And if you try this you'll need a VERY large fin area. The winglets added a lot of spiral instability force that required a big fin to counteract. But on a positive note the winglets added a lot of dihedral effect.