Wow! wildyard, that's amazing. So let's see if I understand. Each t-shirt block has it's own backing (would that be a certain fabric or interfacing?) to which the shirt is quilted. And then another whole backing is used for the back of the entire quilt once the sashings are attached? I use fusible interfacing on the back of each t-shirt square (I iron this on before I cut out the block). The first few t-s quilts I made did not have the fusible and they were too stretchy to do the machine quilting.