Smaller sumps are still practical because they hide your aquarium's equipment and eliminate the need for hang-on-back skimmers and reactors.  It places the heater in an area out of sight, and you can even install cooling fans to help keep temperatures within target range.  The Model E sump was designed for to hold a very small skimmer on the left.

A member from DFWMAS requested I build a sump that would fit in his stand, and give him a big refugium area.  The input is quite small, leaving the return area in the center of a decent size.

Accidentally, I built it .5" too wide, so another one had to be built. Zenya from RC bought the first one, and runs his Aqua C EV-120 in the middle zone, with the output into the smaller area. The water returns to the center via the bubble trap, where a return pump sends it back up.

I added "teeth" to the refugium to help keep the snails in that section, as well as any free floating macro algae.