Hi Don. I use to make T-shirt quilts for customers and I use what you can find at JAF: Pellon #906F. It is fusible interfacing for sheer to lightweight fabrics. I use it because you don't want to add any more weight since the T-shirts are heavy as is. You cut squares and iron it on before you start cutting the s-shirt square. So many different layout.
https://www.google.com/search?q=t-sh...w=1005&bih=600
I like the one that looks like a shadow box giving the T-shirt a 3D effect.
Here is a MSQC video on how to make a t-shirt quilt. Good Luck!
http://blog.missouriquiltco.com/t-sh...ing-made-easy/