Hmm this seems odd...
I just measured the glass on my 20 gallon high, and it's 1/4".
Thought I should mention it, since there is a 13 gallon difference here and my tank has thicker glass than yours.
Just an observation... I would definitely get a bigger tank, my 15 gallon has the same thickness of glass as your 33 gallon.
EDIT: Actually, you could probably just get away with bracing the tank if thats feasible, though you would have to drain it almost completely to do it. Probably making this idea NOT feasible in many cases.