Dear sister,
I just read on www.quiltville.com not to use them. Go on Bonnie's site and read her comments and she will tell you not to use them for many reasons. They have seams, not cotton, not straight, etc, etc. Use all cotton pima for best results. Costs more but do you want a crummy result for all your time spent on the top to put junk on the backing? You should be as concerned for the back as the front. That quilt will live long after you, so, make it the best you have to give and you will be remember by your love for your work. Use quality in all ways, at all times, for the best results. Lin