Hello R_A_B_I_D,
I have done quite fine using 4 inch tubing myself, using it as a flood and drain. I forget the exact plant spacing, but I had 12 spots evenly spaced, for 3 inch baskets, in a 9 foot long, 4 inch wide tube. Using it as a flood and drain system, I didn't need to worry about blocking the water flow as the plants got bigger using the round tubing. Once or twice I had to take off the hose from the pump, and stick a screwdriver in because roots were trying to grow throw the opening. But that only took about 30 seconds.

Slotting the tube and filling it with growing media, VS making holes for baskets is really a personal choice. A slotted tube filled with growing media will take a lot more growing media than using baskets, so the cost of the growing medium is a concern to me (thus, the less needed the better for me). Also the growing media takes up space the roots could be occupying, so the more growing media, the less room for the roots.

With my system, I grew 8 large pea plants (4 on each side of the tube), the 4 spots in the middle were meant for some green beans that never made it into the system. One variety of peas were about 4 feet tall and wide, the other was about 6 feet tall and over 4 feet wide. The root mass inside the tube took over 50% of the space inside the tube. Just make sure you design it in a way you can get at least one end of the tube off, or you will never get the roots out. I had to cut the tube in half, then glue a coupler between both haves with 100% silicone to be able to reuse the tube (witch I now have some peppers in).

As for the choice NFT or flood and drain in a continues bed, both have their advantages and disadvantages. Either way just make sure the growing medium doesn't get too saturated, or the roots wont get enough oxygen. In a tube with baskets hanging in a tube used as an NFT, oxygen to the roots wont be so much of an issue, but water flow might. That's why I like it as a flood and drain. Though with small plants like leafy greens with a much smaller root mass, that may not wind up being a problem even using round tube, and set up as an NFT system..

My personal thought is just dive in. But don't build large setups for full scale, all out production right off the bat. No matter how much you you think about it now, there is no doubt that you will want to redesign your systems later for better efficiency. In my experience, build your systems with easy maintenance (while the plants are growing, and after) in mind. As well as make them easy to duplicate and expand on. That makes them flexible, and easy to scale up and/or down, however you wish in the future (without needing to rebuild the entire thing). Even split larger setups into multiple systems reusing the same parts (and vice versa).

Thanks homehydro. Flood and drain with baskets is my preferred option, so it's good to hear that you're having success with it. Do you have a preferred growing medium for your system? I suppose one of the benefits of using individual baskets is that I can do side-by-side comparisons with different media.

I really like using coco chips. It has similar property's to grow rocks, but holds moisture better. Grow rocks are reusable, but I really hate cleaning, and sanitizing large amounts of grow rocks after the grow. I just dump the used coco chips in with potting soil for plants around the house.

As long as you get the chips, and not the coir. Coir has a texture like potting soil and will easily fall through the slats in the baskets. The chips are about the size of the grow rocks, and don't fall through easily. But they are both the same material (just different sizes).