A shallow water crop saver is very common in aeroponic setups, because of the dedicated reliance on the power supply, pump function, etc. In pure aero, if the system fails to feed for any reason, the plants die. With a S.W. crop saver you can keep the harvest, although it'll be much smaller.
I grow aero with a 24 inch drop, into 6 inches of crop saver, under a 250. I l.s.t them and the difference is VERY noticeable. When you aggressively l.s.t. plants, not being shy about it but leaning the plants every time a side starts falling behind, the lower buds that would normally be airy and very lightweight, grow denser and contribute quite a bit of the final weight.
I don't know what the final length that can be reached is, but i'm sure if you dug up a 12 footer in the wild, with root system intact, you'd have quite a bit of root length there. The historical, general purpose formula for most plants, is that whatever you see above the ground, you've probably got about that, below the ground.
In mine, the roots grow very, very quicky in length until they hit the crop saver below. After they do, they tend to get about 6 to 10 inches longer, hanging in the water, and they bulk up in the aero section until they're about as big around as a 2 liter bottle.
My method is to stack two tubs: when i built mine, i didn't go to the store and buy a couple of nylon machine screws (fine thread bolts) and nuts, and fasten the bottom of the top tub, to the lid of the bottom one, like that: all i did, was silicone heavily, and so far, it's worked ok. After i siliconed i found some voids, and filled those with hot glue; it was a ghetto setup and actually, the thing works just great; although the next time i build one, i think i'll just go to the store and get a couple of nylon bolts and fasten the lid of the bottom one, to the floor of the top one, that way, because plastic is so notorious for not taking glue well.
When you use a fogger, the heat of that fogger contributes substantial heat to the interior of the root zone; and, you MUST buy teflon coated diaphrams to make the fog or they very quickly succumb to the acid environment.
There is another problem with using a fogger, and that is that the fog itself, quickly shucks heat and falls, as a cool, cloudlike formation to the lowest level it can. The offset to this is to drive the fog around, with a fan. My method, is to get a 'spinning disk' cool mist humidifier, and put the fogger in that: the water level in it is kept the same with a float, and fed from a bucket.
A tube feeds the mist(s) into the root zone and at the top of the upper tub, there is a mist filter made of scrubber pad and polyfill, inside a tupperware bowl. A computer fan provides a vacuum when the timer comes on that lifts the fog, and at the same time, keeps the pressurization from making the tubs leak.
A spinning disk humidifier uses vanes built onto it's misting disk. Alone, it doesn't produce all aeroponic fog: but it does provide a very good way to keep the heat of the ultrasonic fogger out of the root zone, and the spinning disk's vanes, designed to push it's own mist, also push the fog out at a pretty good clip. Using the computer fan to lift the mist helps keep it from settling too bad, although i really need a bigger fan.
