I made my tanks for 8x10 from 1/4" clear plexiglass cut on my table saw. You can get adhesives that'll bond the stuff together from a glass place but i used hot glue. Don't use aquarium sealer, i tried that and the tanks fell apart. One 2x4' sheet should make you four tanks for that size if you make them about 2" wide. The best would be opaque abs but it's very expensive. If you agitate properly you won't get poor agitation. go slow and don't pull the hanger all the way out of the developer.

vinny