What you've been talking about has not been clear enough for us (at least me) to respond correctly. Your last post clears things up, I think/hope. You can do what I think you want easily.
Example.....a 3x7 ratio image that I want to print on 5x7 paper. I go to the print module. I select 5x7 paper. Under Image Settings on the right of the print module, turn Zoom to Fit OFF and Rotate to Fit ON.
I set Layout with smallest margins my printer will accept (0.13"). Cell size is 6.75 x 4.75.
I get my exact 3x7 ratio image, without any cropping, with 0.13 margins on the top/bottom ie, 6.75" image and 1.05 " margins on the sides, ie, 2.89" image.
I think your problem has been that you've had Zoom to Fit checked ON.
On larger paper size, assuming you want actual 5" or 7" as the controlling dimension, simply choose 5' x 7" Cell size. It would print, for example, a SQUARE image at 5" x 5" centered in that cell with a 1" margin at one of the opposite ends. It would print a 1x7 ratio image at 1" x 7" if you have Rotate to Fit checked, with 2" margin against the 1" image width.
If I've understood correctly what you want to do, does this clear it up for you?
Brad