This video will probably help:
http://www.hgtv.com/video/ask-alex-q...deo/index.html
Even with the most meticulous basting you may still get some shifting of the layers and pushing or contracting of the sandwich during the quilting process. I have never done it myself and I don't think I would want to try. Many people have "birthed" quilts but I believe birthed quilts are usually just tied or tacked so the issues aren't the same.