String spacing is hot topic for Cigar Box makers.  Some people prefer to space the stings as per a normal guitar so they can play without changing the freting style they use on a standard setup.   Many CBG players prefer a wider string spacing.  This helps to balance the slide.

With a thin neck of around 1.5″ (38mm)  you can space the strings around 0.5″ (12-13mm) apart with the middle string dead centre on the neck.

This leaves a little space at the edge of the neck to fret the outer strings and the spacing is wide enough to balance the slide.