I had to comment on this post. I made my stepson a T-shirt quilt. I took a class, bought the recommended supplies (the interfacing is the point of this comment), and got the top pieced, with sashings and borders. Sent it to my LA'r (my LQS owner and a friend). She called me after a few days with a problem. Apparently, the fusible interfacing had come loose from the back of the T-shirts. She didn't dnow this until after she finished the quilting in the sashing and borders. When she tried to quilt the actual T-shirt blocks, The T-shirts "slid" around on top of the batting and was making an unholy mess. She removed The stitches on the T-shirts and started again. After 3 attempts at quilting the blocks, she called me and told me that she couldn't finish the quilting. She felt terrible and didn't charge me for the sashing and border wuilting that she had done and I assured her that I appreciated all of her efforts. I tried FMQ on my home machine. Wouldn't work, T-shirts slid and streched each time I tried to sew. I finally ended up HANDQUILTING the stupid thing, using a straight line grid. NEVER, NEVER, will I ever make another T-shirt quilt. It was like quilting through plywood. My fingers will never be the same. I have no idea what happened with the fusible or why it came unstuck. Hope you have better luck than I did.

I met a woman while in line at JoAnn on Black Friday. She says that she uses flannel backing and NO interfacing OR
batting on her t-shirt quilts and they've been fine. She said that she does sashing and that holds the shirts stable. I am going to try her method and see how I like it. I have the lightweight interfacing from JoAnn but if I can save a step and still get the same results, I'm all for it.