You want the weight as close to 2.5lbs as you can get.
Wingspan, around 64" or a big longer works well.
Wingarea, over 600sqin is good, you want the lightest wingloading you can manage.

Airfoil, there are lots of options, but you want something with low drag and a fair amount of lift, but most important is a late and soft stall, nothing abrubt. Blunting the wing LE helps with this. (I use my own designed airfoil. It looks kinda like a Clark-Y, but with the high point moved back slightly, and a tad thinner, I think).

However, the most important thing is pilot skill, you can't make up for it with equipment, and all of the competitive designs are really pretty equal.