Wow wish I had a high school class like this! I have a Pilatus Porter airplane with the following wing dimensions Span 52.5 inches and a chord of 7 inches. Your wing size should be fine. I'd tend to think as stated earlier, a flat bottom airfoil would be a better choice. Keeping the all up weight under 3lbs would be crucial. A 10kg load is out of the question. I think a 10 once load would be a bit much in a plane of this size. An electric motor comparable to a .25 size glow motor with lipo batteries would give plenty of power and help keep the weight down. Sticking with a brushed motor and speed controller would help keep costs down.