I was also thinking a 72x10x16 tall might not be bad. I would have a one foot square sump at the far end where I would place the protein skimmer, pumps for circulation, heater, chemical media, etc.
Or, perhaps a 4x12x12 tall sump at one end and a 6x12x12 tall sump at the other end, and a false wall with a 2 to 3" depth along the back. That would be a very long false wall, though, and would take away from the display area. Not to mention, not sure what I would do with quite that much room. Or, I could just have the false wall along the back and not have the sumps at either end. Might make more sense. If I did a 72x12x12 tall tank, that would keep the size in gallons to about 45 but giving it an extra 2" in height would be about 50 gallons. I like the look of a big tank, but this would be manageable and keep weight down. I might need to add some additional support to the front edge of the island counter, but would prefer to avoid this unless absolutely necessary. The counter is about 18" front to back and sits over a 5" or 6" column that runs the length of the counter. I would prefer not to add the extra support as it would really alter the look of the counter, and while I'm sure I could build something that would work, I'm not sure I could make it look nice. Thoughts?