I was asked about the stretchiness of the t-shirt fabric.
(Here is my edited response.)
As far as the t-shirt fabric goes, the light weight iron-on pellon keeps it from stretching while you sew, but it does add a little "stiffness" to the quilt block. No one has complained that it is really too noticeable, so..... However, I have another book that says you really do not need to back the shirts. It is called How to Make a Too Cool t-shirt Quilt by Andrea T. Funk. I have not tried it. I do know that based on what I read, she really did quite a bit of quilting on hers even though she also talks about tying it. When she gets ready to actually quilt the quilt she puts on a temporary binding to help avoid stretching. The backing is 100% cotton, but not flannel, so that would help keep everything from stretching when you roll it, but I am not certain how this works. I ordered the book from http://www.toocooltshirtquilts.com. If you try it, I would love to hear about your results.