As long as there is no pressure on the bottom pane of glass you're good.
I have a 30 on an old work bench that was slightly out of level. I did the same thing.
I'm not good with a saw and let lowes cut my wood which was a big mistake lol. It still came out Close to what I was aiming for. I wanted a taller aquarium stand because I like to stand in front of it and look into it and most prefab stands are only 28" or so tall. I made mine 34" if I remember correctly and it gave me plenty of room for sump maintenance if needed.