I actually installed the butt ribs with cap extension outboard, as stated in the manual. I have had no trouble with this but care is needed because the skylight screw holes are quite close to the edge. To help this situation I trimmed the skylight plexiglass out beyond the edge of the butt rib capstrip by about 3/16" so the plexi overlaps the gap between butt rib and wing rib #1. This all worked out fine, but if I were to do it over again I would reverse the butt rib cap extension to the inside like many of you are doing.