RE: Another Guillows RC conversion - a few Q's
The models I've seen with only rudder for turning use a "cartoonish" amount of dihedral. Ailerons, especially on a Guillows model adds to the complexity to set up. The models you mention would do well set up either way.
I'm not sure what to tell you about dihedral angle, I usually build in what looks right compared to other proven designs I've seen.