In regards to using heat mount materials with canvas, the important thing is to get a thick layer of the adhesive that can flow deeply into the canvas as heat is applied.
One way is to use multiple layers of Fusion 4000 or a similar tissues that are sheets of pure glue with no carrier paper. Since it melts and flows it can be piled up haphazardly with both large sheets or torn up bits and pieces. As long as there's enough of it, and heat is applied long enough so it flows into the canvas, you're good to go. IMHO three layers is minimum for canvas if you want a long term bond. As with any new attachment method, one should test to see how easily artwork can be pulled away from the backing. If the media pulls away with large parts of the backing sticking to it, that's good.
Peronally, I dislike the way heat mounting flattens the canvas texture. For this reason I prefer the good old wet Miracle Muck technique. I have Muck mounted canvases more than 13 years old that are still perfectly attached to their Gator even at the edges.
FWIW dry drymount adhesive and wet glues like Muck are basically the same stuff. You can roll a thick layer of Muck on some Gator, let it dry, then heat mount a canvas on top.
