Here's a helpful thread using information that one of the founders of my club put together. Many, many, many models planes have been successfully designed using his principles. The dimensions he gives don't necessarily extract every possible bit of performance from a design, but they do yield a plane that is friendly to the pilot and flyable in a wide range of conditions. Personally, I wouldn't suggest using any dihedral. Dihedral on a high wing plane is for making it self righting in calm conditions, not for making it carry more weight or be more efficient.

http://www.rcuniverse.com/forum/scra...formation.html