what I would add is to play around with the angle of the butterflys. I found that slight changes made for more comfortable hands, especially when riding over rough stuff with the hands on the predominant position of right at the corner area (same hand positioning as on hoods on drops, or on flat bars with bar ends using the bar ends (ish)
anyway, experiment and see what feels better, and live with them for a while and make changes on the fly.
remember too it may be hit and miss with the stem length angle etc, so good luck mucking about with that variable also.
+1 on the angle. i dont use butterfly bars but with any bars the angle is a big part of my comfort for long mileage days.