I never did find any numbers to use to build mine, I just looked at yours and others and guessed at the height. Your skimmer looks much bigger than it actually is! I haven't glued mine together yet so I can easily cut the tubes shorter. My box is 12H x 12W x 14.5L. My collection cup is 8"H, the neck is 10" total with 4"inside the cup and 6" between cup and mix tube. It seemed that the taller the mixing tube (is that the right term?)then the longer the contact time... am I thinking wrong on that? Would it hurt to have it as tall as I do...it certainly would be impressive to visitors who look at it! I don't mind cutting it though if it would work better since that is the whole point. Thanks for answering all these silly questions!Mine is two inches taller then the Barr i copied. It is rated for 1000+ gallons.
Are you doing the 12" tall mixing box and cup like mine? My skimmers total hight is 50". It's not how tall the skimmer is that makes it perform good. It's the contact time. Another misconception is that people seem to think if they make the bubbles twirl up it will have more contact time. This is not true.
The Barr Ultra Beckett skimmer is the most productive skimmer out there atm.