Good morning, Ken
Very nice tubes you have there. They got me thinking back to my pre-pen days when I included dye sublimated coasters in my booth at A&C shows. A bit of historical perspective FWIW. After purchasing a special printer, a heat press and relatively expensive ink I gave it up after 3 or 4 years. The primary reason was I couldn't print frequently enough to maintain an acceptable ink flow and cleaning with the high cost ink wasn't very cost effective. Unless things have changed dye sub inks needed a polyester substrate or they would not adhere well if at all.
In some ways thermotransfer seems to be a significant improvement, especially if there is no need for the thin PE coating. MY very short Google search didn't provide an answer. I assume you are doing the transfer from the special paper in an oven and are holding it around the tube with tape. I would consider playing around with it if all I had to purchase was some thermotransfer paper,which I understand can be printed with standard ink used in inkjet printers. I'd be interested if you think I have it about right.
Again, nice and very innovative work.
Larry