I took mine to a machine shop with the original gear from the tranny and asked them to make the new gear's bore size the same as the old gear's bore size. A couple hours and $20, done.
I did both. Dropped 2 teeth on the rear sprocket and the OD 5th gear. Would I do it again? Yeah. These trannys are so close geared. Maybe because this was Mother Yammas first 4 stroke street bike and she was used to 2 stroke bikes. Maybe I prefer a wider spaced tranny because I wanted to run this bike on the highway at under 5500-6k rpm. Did I get what I wanted? Close, but not quite. Its still a GREAT "B" road bike!