I'm just setting up a 4 bucket rdwc. I'm using 5gal buckets for the plants and an 18gal res outside the tent. I plan on using 1 1/2" from each bucket feeding into a 2" pvc back to the res. I found the uniseals for $2.18 each for the 1 1/2" and $3.00 for the 2". I don't want to use bulkhead type fittings, I've ran into issues with them leaking before, especially on round buckets. I know for sure the uniseals work very well, and I don't want to experiment with something that may be a little cheaper but may or may not work. This is just going to be a test, I just do very small (4-6 plants) grows and have always used DWC with 5 gal buckets.
I'm not really convinced that RDWC has any benefit over DWC in my situation, largely because I am usually doing multi strain grows. My plan is to do a single strain 4 bucket rdwc in one tent and 4 bucket dwc in another tent and see how it goes.