I've grown squash in 5" net pots inside a 6" pvc pipe and tomatoes, peppers and eggplant in the 10" net pots inside 3 gallon buckets. Both ran drip for a few minutes each hour, not constant like nft so I needed more medium. The net pots had grodan and clay pellets. For things in nft or water culture I would use much smaller since the roots grow out the net pot more. For drip and ebb and flow a little bigger is better to hold the moisture. The medium you use makes a big difference too, rock wool holds way more moisture than perlite or clay. There is no set guidelines I've seen but the plant will let you know if it needs a bigger pot.

Usually just the tips and not more that 1/3 the length when pushing it from what I've heard. If any are diseased, just keep the healthy parts. As for fitting them through all the holes, l'm not so sure about that. It is better to mostly get the roots to chase the water IMO. Just putting the roots in the net pot with a medium like expanded clay (hydroton) should do much of the trick since it wets by itself wicking solution up when barely sitting in the top of the water level. You don't want to drown roots, especially those injured from cutting and having a lot in the more oxygenated medium is better than under water - by far. Others may have better experience with what to do with the roots for a big plant, but I would prefer to cut out part of the bottom nd bring a braid of fluffed out root if I had no other choice, and let the plant do the rest. Since you may have a large plant it might be more complicated. Maybe a different medium like a simple perlite bag system, but that's just mulling. My experience was with different plants and although the roots served their purpose initially, my plants eventually developed new white roots and the older ones eventually dissolved away anyway in a great part which as old organic matter provided microbe food, especially those that were under the water level. But I'm just one data point...

I'm going to guess you damaged the roots during transplant and they haven't recovered yet. Here's my rationale: turgidity occurs when transpiration is greater than absorbtion; since your plants are heavily shaded(or picture taken in the evening) its probably not so hot the plant is transpiring that much. The new leaves appear unaffected; root damage usually occurs to older roots as they're bigger and more likely to get broken and the younger roots are actively growing thus more likely to recover from any damage they receive. Of course it could be over watering is killing your roots thus yielding the same symptoms. you might try something more along the lines of 1/2 on, 4 hours off.

Hey, Cj, thanks for the clarification! I was sure the whole process was a lot more complicated than my stab at explanation, but I didn't expect it to be this wonderful! Of course, even my simpleminded description draws blank stares from anyone I show the flower to (after they stop laughing). Good to know the "real deal." Thanks again! Sharon