I've been using 8-frame sized supers for quite awhile now. Thanks to the idea and inspiration from Michael Bush. However, most recently I've decided that all my new gear, and going forward, will be 14" wide, and with 12-1/2" inner width. I've also configured many of my brood supers, with side-wall inner racks. Even with the racks, a 12-1/2" wide 8-frame super, will accommodate 9 frames, 1-1/4" wide. And the same super, if used without the side-wall slatted racks, will accommodate, ten, 1-1/4" wide frames, hence it is then a 10-frame super.
Can we really still consider these, narrower supers, to be 8-frame supers? It being a combination of the internal dimensions of the supers and the width of the frames, that actually determines how many frames each super can hold. Now, if I were to squeeze ten, 1-1/4" wide frames into 12-1/2" space, there is not going to be the tiniest bit of wiggle room, so that many narrow gauge frames seems quite impractical, but nine frames would fit very well. I find that nine narrow gauge frames fit quite well, even with the slatted side-wall racks. So, even though I call them 8-frame supers, I'm actually using them, regularly, as 9-frame supers.