I really hate it when people who do not understand how print files work set the spec for print file submission.
Now, no offense to anybody, but here's a hint...
There is no good reason to spec out a print file in terms of dimensional units.
There is exactly one unit that is relevant to speccing a print file, and that unit is dimensionless. You do have to know the projected use to set the spec, and that does require knowing a dimension, but that's your job, not the photographer or artist's job. Spec it correctly, please. Thanking you.
M