I have found that the transverse space between strings is comfortable when one uses the same as what you are used to. The thickness and feel of the neck seem to be less important. I would measure the spacing at nut and bridge on your favorite axe (or if you have an old nut-bridge you have replaced). Please yourself! If anyone else says something? (you could listen) or they can build their own!..... .270 at the nut, .375 at the bridge. (measurement on my "good ole" flat top)
My banjos are all set up for 5/16" string spacing at the nut, 7/16" at the bridge. I'm used to it, so I build accordingly. Nice to be able to bend strings without rolling them off the fingerboard, so I add a little extra neck margin, 3/16" isn't too excessive.