You can reduce the wide radius corners a bunch, your seem to chew up the porthole size. You could use a piece of 2" PVC as template. If you're using 1/2" material, you wouldn't need the center brace. Just trying to help you get in and out of that tank. J
The top back and sides are 3\8 and the front panel is 3\4. I want it to have as little bow as possible think it would be fine with out the center brace? It's my tank by the way pepperdeath was kind enough to start the thread for me.