When I mat prints, I float mat borderless dry-mounted prints. I leave ~ 3/8 inch of space between the print edge and the window mat on 3 sides and a slightly larger gap of 1/2 inch on the bottom of the print to sign the matboard. I center the print horizontally (of course) but position it slightly upward vertically so that the bottom margin of the window mat is larger than the top margin.
That works well, but is a bit tedious in practice. Also, it means different dimensions for vertical vs. horizontal prints. I am preparing for a large frame order so I have been toying with the idea of ordering pre-cut mat windows such that the print would be centered and the "float" margin between the print and the window mat would be the same all around. That way, I could use the same mats for horizontal or vertical prints and I could use a single jig for positioning/centering the print for dry-mounting.
Good idea or bad idea? Thanks.