An uneven tank places stress on the glass, & over time may cause the seam to fail. 3/4" is too much for my comfort. I would shim it just to be safe.
80 gal FW with 30 gal DIY wet/dry/sump.
9 fancy golds, 1 hillstream loaches, 1 rubber-lip pleco (C. thomasi), 3 SAEs, small school of white cloud minnows, planted.