For construction tips, visit
http://www.airfieldmodels.com/. Some of it won't apply to your project, but this guy focuses on making things as light and as strong as possible, regardless of how much effort has to be put into it. For your project, a truss type fuselage makes a lot of sense with either a foam or built up wing. Foam is faster and easier to make (especially since you are scratch building), while a built up wing is lighter. You may even consider using foam for your prototypes until you get the performance you want, then design a built up wing to replace it in order to take that extra few ounces off of your unloaded weight.