I made a second a few weeks ago. Find some 8-inch pvc pipe. Use a jig saw to cut a section from the pipe. I cut mine to be shaped in an hour-glass configuration to reduce weight.
The pipe is very strong. You only need a width of pipe of maybe 5-6 inches max to "cup" the tank. I drilled two holes along the centerline that match the wing and backplate.
I bolted it to the backplate sandwiching the wing in between on a somewhat permananet configuration. The pipe wall is thick enough to allow you to coutersink the bolt heads..I used bolts with very wide flat heads from the hardware store. I also used some Corning 5200 adhesive to make the contact area between the STA and the tank, less slippery. Just put some dabs of material, here and there. Pretty simple.
If you do not have 8-inch dimater pipe, you could use 6 inch probably, cut a section and then if it is too tight to cup the tank, put the pipe in the oven at 325 for 6 minutes and until it gets soft, then using gloves remove it, lay a tank down, place a towel over the tank, and then lay the pipe over it and press on the pipe as it cools so it conforms to the tank diameter.