Hey what about Graupner props? I seem to get great results with those on my YS 4-strokes.

Shouldn't the small tips on APC props be a concern since they push very little air volume? So a 15x8 APC is almost equivalent to a 14x8 Graupner or MA since the tips on an APC do little work. Maybe this is why APC props generally spin at higher RPM than the others because in effect, APC props have "smaller" effective diameter.