I have done this on several tee-shirt quilts when the customer had many, many shirts. i designed the front with sashing and using the most important tee-shirts. For the back I used all the rest and just sewed them side by side. In other words, there were more, less interesting tee-shirts on the back. This also eliminated any need to line things up. I interfaced all the squares with fusible tricot interfacing. Yes! The quilts were very heavy, but each one was very well-received and resulted in repeat customers.