I don't know the answer to your question, but I am thinking on it. I know that I have always been told to not use polycotton because it shrinks differently than cotton...but you would think there would be a way around that? If your quilts are made of warn and washed clothing, then you would think their shrinking days are over. If you washed the red....which you would want to do anyway since red fades....you would think that would be "shrinked" as much as it was going to.
I did put polycotton on the back of one of my recent quilts because the color was just right. I haven't washed that quilt yet though. I know that isn't much help, is it?
I will be reading this thread with interest to see what someone more experienced says. (I have only been quilting 3 years.)
Dina