I actually just finished a sump/refugium that I'm happy with. I'm also thinking of building 2 skimmers; the one for the course and a smaller one (4" tube) for smaller systems. Right now on the market there seems to be either large beckett or downdraft skimmers suitable for systems larger than 100 gallons, and the little guys like remora/urchin/prizm etc. that are driven by powerheads. These skimmers don't work well for anything but the smallest systems, IMHO. I have an urchin, which costs $160 (not cheap!) for my 45 gallon reef with 3 fish, and it's barely adequate, maybe. So what's out there that's right for 55-75-90 gallon systems? Not much. I'd like to make something that will work well with a 500pgh pump, not take up much room, and really be effective for these mid-size systems.
Matt