Tnkrer, no, I don't use the yogurt cups as net cups. You have to look/think at the geometry in cross-section and make sure that whatever is being used as the "wick" has a good seat/submersion into the water level in the pvc pipe. I use 3-in Hydrofarm netcups that are super economical and good quality - I get them on amazon.
The potting mix depth is just a factor of how much you put in it and how HIGH the raised bed frame is to hold the media in. I used decking planks so I think its 5.5inches for me but you can see in the pictures, the mix settled and I still did great in probably what was around 4-inches of mix.
The raise bed planter does just sit on top of the rggs rig.
I don't know what you mean by the 2x4?? You'll be surprised by how much structure the metal hardware cloth gives you. This bed is 16-inch wide. I probably could have made it 18-inches but obviously if you get wider, you'll need perhaps a 2nd rig below it. So along with stapling it to the underpart of the interim braces, the whole middle is supported by the wood frame of the pvc rig (the 2x6.) That's why no buckling. I hope this section helps. And also think in plan about all the supports that contact the hardware cloth.
This year, I'm planning to experiment with the other Larry Hall brainchild - the kiddie pool concept. For me, it'll be boot trays with 1 gallon grow pouches sitting in 1/2-inch max of water at all times. I'm going to cover the exposed water with pea gravel.
I have seen other ways of making sub-irrigated raised beds that involved drainage pipes/ sand etc. For me, this method was just KISS...
Let me know if you have any other questions.
