Ok, to answer the questions you asked:
The glue I got a small tube at Target - I'll have to go find it and tell you the name, but it is just a tube of cement type glue. It went on white but dried clear.
The legs do not adjust - I couldn't find legs that did adjust.
The corners - I haven't actually made a large quilt on it yet - so I can't address that. I imagine the corners could be sanded down.
It doesn't shift - but again, I haven't done a large quilt on it. I did however, use heavy duty velcro. I put a piece on one edge, a separate piece on the second edge. Once that was stuck on, I cut one large piece that attaches, and connects the 2 separate pieces, so it doesn't shift.
I think I answered all the questions. I will go look at the glue and get back to you. I've been MIA the last few days and this is the first chance I had to check in! :-)
Thanks for all the comments.
O - one more thing you asked - the plexi is the only one Lowes carries that isn't flimsy. It's about a quarter inch thick I think. I will measure the one piece that is not cut and tell you the size. Give me a couple of hours.
Thanks again! (yes, I AM proud of myself for making it)
Martha in VA