Due to the lack of space, this sump was built in two parts so it could be installed more readily. The skimmer and return zone are in the shorter sump, and the taller vessel is the refugium. The sump is 28" x 14" x 14"( or 23.8-gallons) and the refugium is 10" x 14" x 18"( or 10.9-gallons). When running, the combined volume of both parts added up to about 23g of water.
The refugium was inserted in the stand first, and moved as far to the side as possible. The sump was inserted standing on end, then rotated into position. Once this was done, it was plumbed. The skimmer went in the left end, the return is the "middle" of this layout.
Two bulkheads were designed for this taller refugium, mainly to handle the flow if one were to clog for some reason. These were plumbed so that the pipes would drain in the bubble trap to avoid microbubbles in the return area.
The sump was quite narrow, due to the stand's restrictions.
Since each unit was small, the flange (top edge) was kept to 1.25" wide for easier access.