It sounds like you are generally happy with your pin basting process, but you might take a look at this technique by Sharon Schambers. I had terrible trouble with puckered backs until I tried this method. You do have to find boards the appropriate size for your quilt, but the rest is so easy compared to pinning or otherwise hand basting, and you can do it from a chair instead of on your hands and knees.
http://www.youtube.com/watch?v=HyaLs..._h42qQ&index=6