Though we've never communicated directly, GPSFrontier has been a huge inspiration and help as I finalized this system, so thank you, GPSFrontier! This thread provided the final bits of info I needed:
http://www.hydroponicsonline.com/for...rd-system.html
I'm using General Hydroponics Flora Series
nutrients in a 30 gallon tub filled to 20 gallons. I have a 185gph EcoPlus
pump on a timer, and will be adding the air bubbler in the next few days. Each tube handles 13 plants at 8" apart, though I still have to populate the second tube. I started four kinds of lettuce in a Rapid Rooter 50 tray (about three times, since I kept killing them somehow). I still need to mount the timer and air pump under some sort of waterproof cover.
I flood/drain from one end with black Dig tubing off the pump, and overflow on the opposite end. The overflow height is adjustable, since the caps are non-permanent, sealed with a rubber band around the tube, and the overflow is off-set from the cap center.
I have a cheap HM Digital TDS-EZ meter and a simple GH pH test kit.
So far the plants haven't died, which is far better than my overall luck with the starts, but it hasn't even been a week yet.