With that little bowing out, I think I would make 4 glass triangles about 2 inches on the side going against the end glass, and about 6 inches on the side going to the front/back glass. Then glue them in and I don't think there is any chance of problems. For safety I would knock off about 1/4 inch of the sharp point on the triangles, and break all of the corners so they aren't sharp. The corner braces should virtually eliminate the bowing.
I'm assuming that the tank won't come apart in a week of testing. To "proof" test it, push out on the front/back glasses with about a 1 pound push. That should increase the load on the glass by about 50%.