Small electric models made of foam are a great way of checking out a design. There are a lot of designs made by the GWS company that are great fliers. They are all molded foam bodies and molded wings. I have built quite a few of them and they fly nicely. They are also inexpensive. Buy one of the full bodies models, build and fly it. It will give a great handle on what is possible in foam. You can check out wing areas, fuselage shapes, tail sizes, etc. in a smaller scale model and if it works well then scale it up and do a balsa build.