Why the 31" scale? Just curious.
I'll try to keep this short - I have a Conklin 9 string that has 19mm spacing, a Bill Dickens at 16mm, and a Galveston 8 string unpaired bass that has 13.5 spacing. All are 34" scale.
I'm fine with 34" scale length but would also like 35" as it tightens things up a bit; helps with picking in the Christian metal band I'm in. I've been playing the 9 on my worship team and it's too wide - 16mm would have been better, or 17mm. I'm used to the Bill Dickens but now I feel like I'm missing a string or two up top.
I like using the 8 string with the metal band as it's easy to transition from string-to-string but the spacing messes with my muscle memory when going between different basses. My main bass with that band is a custom 5er w/19mm spacing. If I could, I'd probably have them all at 17mm and either 34 or 35" scale length as that would simplify things.
I can slap on the Bill Dickens as I'm used to it now; takes a little more attention to detail on the Galveston with the narrow spacing. The 9 string is easy - but again, muscle memory screws me up. Been trying to play it a lot more though.