Modeling industry uses 9x12 as its standard for photographs. The legend has it, it came from the fact fashion shoots were often done with 645. perhaps this is the reason. I use this 9x12 with 1" border all the time as it meets my vision quite well.
Actually, 645 and 6x7 (and 6x8) works quite well to print on 8x10 and 11x14 with very little cropping. Keep in mind, the film opening on most neg carriers (on enlargers) do crop a bit, so you'll have to take that into consideration as well as minor framing errors when shooting.
Yes. I've seen a lot of 9x12 work in model portfolios, so one might opine that this is where the demand for 645 format came from.
My enlargers show the full neg area, btw. It's strange they would crop the neg.
"Often moments come looking for us". - Robert Frank
"Make good art!" - Neil Gaiman
"...the heart and mind are the true lens of the camera". - Yousuf Karsh