Shrinkage

I'm still having trouble with knowing how many inches to put in the quilted length and width with the different battings.  For instance with 100% poly, 80/20, 100 cotton, etc.

I have a quilt measuring 82 x 104.5 and am using 100% poly.  I need to know what to put in the quilted length and width. 

If I put the quilt on the frame, put 83 in the width and 105.5 in lenght.  then do an edge to edge and measure how much it shrunk, is this a good method or is there another way?

Thanks.

Carol Osburn