I'm with you on the 30 inch height I was planning on doing that too, but every time I siphon my 24 I thank thank the stars I didn't do it either... lol
The bottom seams are under the most pressure, but they normally fail due to a bad weld.
Your seams are still intact, so I would think it has to do with either bad material or bowing?
$1700 seems crazy high for a tank that size, but it is custom.
If your up for it you could probably repair it with "Euro bracing" the bottom like this glass one.
euro.jpg
Just cut pieces to fit the edges and glue them in with Weldon 40.