Hello cable24601,
The hydroton is to large to fall through the slats in the baskets, so the baskets themselves will hold them in. If using a
growing medium like vermiculite, then you would need something like cheesecloth to line the baskets. I like using coco chips myself, a couple pieces of it will fall through at first, but they stay in just fine. I attached a pic of my 3 inch baskets with coco chips in it. The
neoprene inserts are used to plug up any holes for baskets that you aren't using. That way the water doesn't evaporate through the open holes. Also so nothing can get into contaminate the
nutrient solution, or an easy opening for pests to get at the roots. They can also be used to support small plants when not using any growing medium, but when they get bigger the plants will wind up to heavy for the inserts to support them. Another thing they can be used for is to place on top of the growing medium. Not to keep it from falling out, but to keep algae from growing on top of it, and/or to keep pests from getting access to the roots.
If your concerned about the
grow rocks from falling out the top if you plan to be moving the baskets a lot (again I use coco chips so that wont be an issue for me). The neoprene inserts cost $0.95 each, but you can easily use much cheaper alternatives like Styrofoam (a small soldering iron will cut it like butter and eliminate those small pieces from falling off), or cheesecloth, or foam insulation (cut to fit) etc.. You just need to make a hole in the center that will be large enough to accommodate the trunk of the full size plant, and cut a slit down the side to allow you to put it on and take it off. Even so, I don't think there would be problem with having any grow rocks falling out the top of the baskets, even moving them around when growing small wide plants like lettuce and strawberry.
There wont be any issues with the baskets themselves falling out. If you really wanted to, you can easily create a slid clip using a small piece of plastic or metal. Screwing it to the main tube near the bottom of the baskets (using stainless steel screws). Then just slid it over the lip of the basket to hold them in. I don't see any clips on there system, and I think that would be completely unnecessary, even for taller plants. Take a look at this picture of their system growing peppers, click on the picture for the large version of the picture. Then look at the basket in the center of the far left tube. It only tilts about a 1/4 of an inch. That's about all they will tilt. In fact that's a benefit to me.
http://supercroppers.com/wp-content/...3/IMG_0144.jpg
The reason I want to use square tubing and not round tubing, is so that the water level in the tube when I flood the system can be higher without leaking out, take a look at my attached images of round VS square tubing. When the baskets tilt like that, the bottom of the baskets will be even farther down in the water. If your worried that as the plants get larger and somewhat top heavy they might be more inclined to tip/fall over, the root mass inside the tube will hold the plants in place. Take a look at the image of the plant's roots in the basket that are growing in the tube. On larger plants the root mass will get so big you cant even pull the basket up to look at the roots.
P.S. That brings me to a design hint.
Make sure that you can open at least one end of the tube. Don't permanently glue both end-caps in place. If you do, you will never get the root mass out of the tube without cutting the tube in half. Like I had to do the first time, then you'll need a coupler to reconnect it later. See how big the root mass was for my peas? The root mass on that side of the tube was from only 4 dwarf pea plants (about 4 feet tall). I Had to pull the baskets up as much as I could and cut the roots off with a steak knife until I had them far enough out that I could cut the roots coming out the bottom of the baskets. Then I cut the tube in half with a hack saw to get the root mass out of the tube, and clean the inside for reuse. I would suggest sealing at least one end with just 100% silicone to keep it in place, and water tight. Then you can just use a wooden dowel and a hammer to pop it off later to clean out.