I've used commercially made frames of the normal 1 3/8 inch center to center type and have several of them in use now. I also have made my own frames on a 31 mm (about 1.25 inch) center to center design. This was based on an article in the January 1977 Gleanings by Charles Koover. The narrow frames can be fitted 11 to a brood chamber as compared to the standard 10 per.
I'm curious if anyone else has used narrow frames and if so what results you obtained. Note that I have a pretty detailed writeup of the results that I will post if this topic seems worth the trouble.
Given the amount of interest in small cell foundation, it makes sense that the slightly smaller bees would perhaps be better fitted to a narrower gap between brood frames. Note that narrow gauge frames have no benefit in supers.