I purchase a high quality double sided drafting mat. I have about 6 of them right now and get them for all of my quilty friends....just a suggestion, I buy mine from a college bookstore. They are double sided and professional grade. My daughter brought some home and managed to put them in her car apparently on top of some items for about a week. I have had them downstairs for a few years now trying to get them back in shape. I was just about to cut them down smaller when the weatherman announced that it was going to be 100 today. I put them on the lawn on a sheet for about 5 hours, till they just about felt like they were melting. Then, one at a time, I brought them in the house, laid them on the linoleum floor and completely covered with heavy books. I did this a few days ago, but it was only about 82 and I didn't leave them out long enough. I will peak at them in the morning and see what happens. I figure the AC will stiffen them up again....I hope.