I have a commerically made Acyrlic tank. It is 8 feet long, but only 2 feet wide. It is 30" tall (300 g).
However, the top is acyrlic with 3 access holes in it.
I think you could probably go 30" with 3/4" acyrlic IF you had really good bracing across the top.
But I am not an expert, I'm just someone on the internet giving you one more data point to consider.