On another discussion list there was a case where someone had built a highly modified DB with no dihedral (it did have section thickness taper dihedral) and no wing tips. The pilot was having all sorts of trim issues. In other words, the dihedral that the designer settled on is probably the best choice. Especially, if we're talking about people like the Prettners. If I were building one I'd go with the 3"/75mm called for.