Take a look at mine at indoor its 24x24xI think 16 or 18 high it is 3/4 and 1/2 I think I would do all 3/4 sides if I was going to do it again with 1/2 only on the bottom just a little bit of bowing with rimless and 2, 1/2 inch sides. I think if you went 3/4 you could probably get 24 square without any trouble so 20 high should work great I love mine check it out when you get a chance has cherry stand granite top 400 halide pendant closed loop and double sump might get some ideas of what not to do and maybe some of what might work