Zoo,
I add 1-1/2" to the measurements of my project which I find to be amble if you are hand quilting. However, if the project is to be machine quilted on a longarm, they need the extra in order to stretch the fabrics/batting onto their equipment. Machine quilters will quilt off the edges of your project which I find helpful when binding.
I recently had a wonderful experience with a longarm quilter who obviously had a stitch regulator on the sewing machine. She did an excellent job and the turnaround was quick. She charged $88 for a queen and also paid the postage to return my quilt. She had an excellent variety of patterns from which to choose. I will repeat with her.
If you are interested in her name and email, please PM me and I will provide same. You will not be disappointed.
Suz