Does anyone on here know what shrinkage rate to figure when using acrylic yarn for weft? I am working on placemats for a friend - who wanted to match some placemats her mother had woven years ago. Her mother used crochet thread for the warp and acrylic yarn for the weft. The original placemats are approx 13" in width and 17" in the length. When I did a computation on on-loom tension vs off-loom tension, I came up with weaving the placemats 15" wide an 20" in length. Now that I have removed 5 of them off the loom, they are 14" wide - which is fine - but still 20" in length???? What in the world is going on?? Help, please. Thank you.