cutting a 30 inch tall tank to 24 inches tall.

[sphelps]

Wear safety glasses!

BTW all 230 gallon standard tanks bow out from the center like you described, basically poor design as the glass should be thicker and braced better. If it has 1/2" glass and a huge center brace in the center it's the standard 230. It will still hold water fine, it'll take more than a little bow to separate those seams.