The best tube benders I know of are the Ridgid brand, but they are quite expensive. Years ago, I bought 3/8" and 5/8" ones when they were relatively inexpensive and I was making all kinds of stuff out of 5/8" ski poles or Jansport tubing or 3/8" tent pole tubing. Have also bought cheaper ones from the mail order tool companies for use on other diameters.
The problem with all of them for something as highly tempered as the Easton tent pole tubing is that the radius of the bends is not large enough to bend the tubes without splintering or at least weakening them.
Roger calls his gizmo a Rolling Jenny, and it makes a very high radius bend with repeated passes. Suggest you email him at Roger@backpackinglight.com, and he may be willing to send you a photo. Right now he is probably buried in testing the oodles of fabric samples Richard sent him, not to mention his upcoming articles, and of course, he likes to get out now and then. I am spread pretty thin myself right now, so know how it feels. What ever happened to the retire in retirement?
After my last message to you, I decided that the best way to make a frame for a suspended mesh backband might be to use a tent pole hub such as can be bought from FibraPlex. They sell undrilled blanks, so you can put the holes where desired on the perimeter. Instead of carbon tubing, I would use solid carbon rod, also available from the kite folks, and get just the right stiffness to bend or bow enough to hold the four corners of a mesh trapezoid back panel extremely taut. If the carbon were too stiff, there is also the 1/4" fiberglass rod that is common for flying pennants. For the outer ends of the rods, I would probably use the pole receptors I use for carbon tent poles. The receptors are made by taking apart a swivel hook, and using the bottom half that takes 3/4" or 1" webbing or tape. There is a photo of one in my XX tarptent April MYOG post. These would accept the ends of the rod, as well as grosgrain or twill tape sewn to the corners of the mesh trapezoid. This would be a pretty sturdy frame and very light. My only concern would be whether the acetal receptors would hold up. Of course, one can always sew sleeves of heavy fabric, as Jansport and many others used to put into their packs to hold the ends of aluminum stays; but that approach doesn't appeal to me for a number of reasons. I have some fairly heavy duty 1" swivel hooks that might work well for this application.
The purpose of T connectors would be to secure crossbars on a ladder shaped frame; but as you can see from the above, I'm now thinking of something different. If you want to see an idea for a potentially cool mesh backband, go to a Subaru dealer and look at their mesh back rests. Of course you could also just look at the back of an Exos or similar Osprey pack to get ideas.
Hope this is helpful. Please let me know at firstname.lastname@example.org if Roger doesn't have the opportunity to send you pix of his Rolling Jenny, and I will ask him for permission to do so.