Mounting/matting framing issue

[The_Traveler]

OK, I have this picture http://www.thephotoforum.com/forum/general-gallery/342522-chess-checkers.html that I am contemplating having printed and framed, first 16 x 20 for the artist and then 24 x 30 for me.

After thinking about this a bit, this is my solution to the difference in percentage covered by the mat.

on a 16x20 print, the actual print size visible is 15.5 x 19.5 so I will reformat the individual images to allow the grid of the image to be seen completely at that size (actually I'll make the actual coverage slightly less to be certain).

Now on a larger print the proportion under the mat edge would be smaller compared to the picture so that would mean reassembling a grid of completely new elements - not what I want to do.

So, what I plan on doing is formatting the larger image with the under-mat proportion of the smaller image. That will leave a tiny and fairly unnoticeable margin of white all the way around on the bigger image but that would allow me to make one new grid and use it for all 4x5 sizes.

Does this make sense?
Am I missing a simpler solution?

Does anyone have another idea for matting/framing?

TIA,

Lew

 

[KmH]

What if you just customize the size of the mat window?

 

[The_Traveler]

I've asked and they can't guarantee more an 1/4 inch way.
Considering the image, I am better off leaving the margin a bit loose and getting standard size.