Well, although I've been going mainly on advice from this guy, we've had to make some deviations.
First off, he wasn't very specific about how to run the carbonator, but the operations manual found at McCann's website specifically states that the tank should be filled basically all the way to the top before pressurizing with CO2, possibly because 14 PSI of air will reduce the effectiveness of the dosing. I plan to try this as soon as I can. I meant to connect a secondary valve today so that we could shut the water off without dragging the refrigerator out from the wall, but I got the wrong fittings. It'll have to wait til tomorrow.
However, we've made an interesting discovery: our local Smart & Final sells bag-in-box soda products. Boneville guy had a hell of a time getting accounts with the companies that sell this stuff, whereas we can just pop down to the store a couple blocks away and pick up boxes as we need them. Score!