On the subject of cutting the quilt back, I recently took a class by Renee Haddadin where she talked about that. I had always heard too that ripping the ends made a square back, but as she pointed out - IT DOESN'T! She demonstrated this by ripping a small piece of fabric and then folding the fabric in 4ths keeping two sides together, it was pretty obvious that the ends hanging down were not square! She showed us how to correctly cut the backing at the class and I thought she might have a youtube video on it but I couldn't find it. However, this is a pretty good tutorial on it if your interested in looking:
http://www.quilting-tidbits.com/quilt-backing.html. According to Renee it is very important to have a square back!