Just comparing notes really. I was thinking on my next run after this current one to use like fishing net to line the inside of the buckets so it holds the roots together inside the bucket. However, I use a much smaller pipe in mine but I think the trick was setting the first buckets holes the highest and letting them drop little by little each you go to the next bucket and so on. I think it helps the pump somewhat since gravity helps aide the movement of water through each line and bucket. Do you find the plant stunts at all when you cut the roots? I've heard people swear by it but I never had balls really to cut into a root ball. I guess it's no different then really as in soil I'd open the root ball some when transplanting to another pot. I bet you are adding 5 gallons a day of water when they are in full late flower lol.
I'm not sure what you mean when you say you're gonna line the buckets with fishing line. All i can think is your wrapping fishing line around the net pot to hold the roots tight to the pot and plant. If that's the case, maybe you could get away with using a hair net. I'm would think the roots would grow thru one pretty rapidly.
Idk if having the holes drop in height on the sides of the buckets would make much of a difference with the added water pressure above the holes.
Cutting roots ain't no thang. Plants usually don't miss a beat though i would cut off more than a third of the root mass at once. Like i said, i like trimming the "runner" roots back in veg. It keeps a much tighter/denser root ball up close to the net pot.
As for the water consumption, truthfully they seem to drink the most water from week 3 thru 5/6. Really it depends how much foliage is left on. If there's no leaves to traspire then they can't drink. Usually at peak consumption they'll drink 3-4 gallons a day. It also depends on how much of the roots are covered in water. I've noticed as the water drops plants can't uptake as much.