[fdi]

Yay. Done!

Image dry mounted on 2 ply mount board. Which is attached to 1/8" form core board via photo corners. Matted with 4 ply mat board then into a Nielsen frame and behind a glass.

Looks good actually....

1/8" looks and feels sturdy enough for this application of 9x13" image on 16x20 mat board and frame.

Assuming your are using something like 2-ply rag board for the mounting board it will also be more archival than foamcore which is important with dry-mounting since you have not permanently attached the print to the mounting board. If the foamboard gets contaminated or warped over time you can easily swap it out with a fresh one.