Thanks for posting the pics Ben!

The fabrication instructions (short form) are:
1. cut a length of tubing that will form the size circle you are interested in making, remembering that Circumference = pi x Diameter. Join the cut ends with an appropriately sized connector ("nipple").
2. drill holes in the tubing circle approximately every 10-12 inches. The holes should be slightly smaller than the thickness of the "goof plugs". Or the holes can be made with the plastic tool that comes with the "goof plugs", but this tends to get a bit hard on the hands!
3. cut out a circle of your preferred solar cover - we chose ours because it was the least ugly, to our eyes. I found it helpful to cut the circle slightly larger than I needed so that I could trim it to fit perfectly after it was attached. This also meant that it didn't matter if my initial cutting was a bit sloppy!
4. with the tubing ring on a hard surface, place the cover wrong side up over the rings and squish the plugs into your predrilled holes. You will probably need a pair of pliers for this.
5. trim any excess cover, or any overhang where the ring distorted while you were messing around trying to get the plugs to go in, and then chuck your finished disk into the pool.

Other things: When you take the disks out of the pool don't put them on grass, or at least cover them with a towel, as the sun will fry the grass in a very short time. If the disks are piling up in the pool because of the return jets you can link the disks together to make a big flexible raft - I use the Velcro tape sold for tying up plants because it is both water and UV resistant. The large headed "goof plugs" are easier to use and theoretically hold the cover on more securely, but they are also much more expensive than the small headed ones. I used a mixture and have had no problems with the small headed plugs so far. You can buy them in large quantities online; everything else is readily available in home improvement centers.

I have detailed instructions (in the form of scanned documents) which go on for pages, if anyone wants them, and if there is a sensible way of posting them.

Alison