I have been running this type of system since 1986. I attached rain gutters to the sidewall of my commercial greenhouse. Three rows on each side, 110' each. They drop 4' over the length of the run. I grow lettuce, basil, peppers, and melons in them. They use up what was just unused space in the greenhouse and the cost to run them is minimal. The produce I sell from them virtually covers my yearly operating expense for the entire greenhouse.
I made lids for mine out of sheets of corrugated plastic. You can get 4'x8' sheets from most plastic suppliers and simply cut them into 4"x8' strips and then use a hole saw to cut holes at whatever spacing you want. I have found the 1.5" rockwool cubes are all you need and they cost less than the 3"!
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First picture is the lettuce I grow, second is basil, third is yellow and red ghost chilies, and the fourth shows the whole system attached to the sidewalls. I have grown just about every type of plant imaginable out of these except for root veggies. No photos of cannabis but it grows just as well with this type of system.