Questions:
Has anyone here tried to mount masterboard under /on plexiglass? I'm thinking about doing so and I'd like to hear what anyone else has to say about it.

Second, I've been through all the scaling and troubleshooting. I'm certain my settings are correct, but when I measure a single masterboard block to verify, it's actually 1/16" short. I just want to verify that the correct size of a masterboard square is 6 15/16" x 6 15/16", not 7" x7".

How'd we miss this one? Glad to have you with us, Hadrian!

The only issues I can think of as far as mounting under plexi would be 1) glue would likely discolor or distort the textures, 2) plexi tends to bend very easily, and could tear or separate form the cardstock, and 3) plexi scratches very easily.

1 & 2 can be solved by simply laying the plexi sheet over the masterboard, reather than gluing them together. 3 is tougher, since you'd want to replace your sheet every so often.

I can't think of a compelling reason to mount the tiles on top of the plexi, because of the bending.

If you've tried a sheet, please let us know how it turns out. I could be absolutely wrong, and it could turn out to be The Next Big Thing! Good luck!