I have quite a bit of experience in settling tanks and their design (I am a registered Civil Engineer). I built a special settling chamber for my exterior Koi pond that was basically an open tank, let's say 42" wide x 24" high in cross section. The business end of the settling chamber consists of hundreds of 1" thin wall PVC pipes laid at angle of about 1" rise per 24" run. I made the length of the pipes all 24" long. In theory, the particle has to only drop 1" to be laid to rest on the pipe bottom for it to be removed. It works quite well.
However, I would suggest an easier solution which I chose for my indoor 535 gallon Cichlid tank. Try either making, or finding a shallow pan say 3'x4'x 6 or 8" deep, or however big you can tolerate, and make a false bottom that can suspend an egg crate layer upon which you line with replaceable polyester fleece filter material. This is what I have, and it works fantastic, my water is crystal clear, I replace fabric about once a week. Of course, to keep noise down, the inlet to the filter box should be submerged, and the outlet pipes should employ Dorso type inverted elbows, again to keep noise down. Your assessment is correct about getting out as much detritus and waster prior to biological media, you'll rarely have to clean or rinse you bio media.
I also have a continuous water change system of about 50 gallons per day, but my ammonia is 0, nitrite is 0, and nitrate about 10 -20. I hardly test any more because the community water supply nitrate is just about 10-20, so I don't sweat it.
I have a technical drawing I made on AutoCAD which I could send you as a .pdf if you like. Sorry, I didn't tank any pictures while building it, and a picture now really wouldn't help too much.