On a 6x7, 127 is a "wide portrait" length -- roughly like a 70 mm on 35mm film.
I quite like the 6x7 format (probably in part because it's virtually the same aspect ratio as 4x5), but I doubt I'd seek out a 6x7 back for my 4x5 Speed Graphic (I've got Grafmatics, double dark slides, and a 6x9 roll film holder for it). On my Century, by contrast, an RH-8 was what was on it when it came to me, and that's the most likely alternative to the full 2x3 format for my use.
I quite like the 6x7 format (probably in part because it's virtually the same aspect ratio as 4x5), but I doubt I'd seek out a 6x7 back for my 4x5 Speed Graphic (I've got Grafmatics, double dark slides, and a 6x9 roll film holder for it). On my Century, by contrast, an RH-8 was what was on it when it came to me, and that's the most likely alternative to the full 2x3 format for my use.