I suggest that you use the clear vinyl that is sold by the yard (at Joannes maybe even walmart) it is used to cover chairs or bar stools to protect the fabric from spills. ( I remember when I was a child, a neighbor covered all her furniture with it, yuck.)you the can draw and erase with a dry erase marker until you are happy with your design. It was used at the long arm quilting group I was in. They had a meeting where you could bring in a quilt top and could get suggestions from the "pros" in the group and they used it and you could then take it with you so you could remember their suggestions. It was one of the best meetings they had at least for me when I was first starting out. In fact I would love to do that again.