At the top of preview: "Page: 7.147 x 6.897 (720 x 720)" That's almost precisely the inch size of the 230,230,230 background...

I don't know what this means?

R2400 - Printer paper 7.375 x 7.125. 6-up 2x3's w/.03 & .06 borders = 2.18 x 3.18 with .16 space between & .16 margins TBLR.....which adds to the 7.147 x 6.897.

I don't know what this means.

Max printable area is 7.147 x 6.897... so what adds to it?

Here's what I get

I set your page size to 7.375 x 7.125... leaving me a printable area of 7.147 x 6.897

Now I add 6 vertical 2 x 3 prints, and add to them, 2 borders with a combined width of .09 inches, which when they surround the 2 x 3, the 2 x 3 becomes 2.18 x 3.18

I add the gray page color, and I print to file. Works perfectly!! See screen snap.

Here's where you lose me.

Automatically, Qimage spaces the images properly for evenness .

So automatically, by arithmetic, I get a left margin of .27 and a right margin of .27.

Add 3 images of 2.18 inches wide (6.54) and I get used width of 7.08, leaving unused space at .067 inches..

I need space between image 2 and three, and another between image one and two.

My left over space to work with is 0.67 inches..... splitting that for the needed spaces between Image 1 & 2 and 2 & 3, the spaces are going to be 0.032 inches

Hope this helps

Fred