It’s for a 60” tank/stand.
Wanted to line the rear overflow drains with the fleece roller section and then have a section for a skimmer, small rodi chamber and two return pumps. Along with Having a small space in the corners for live rock or media and two manifolds on each return for algae reactor, carbon, calcium etc.
The drawing is not quite to scale, but I think the general idea comes across. And it’s not 12” on each side, more or less 10-11” on each side. Or may be better to line it up left or right and have 20-22” of space on either side?