I would definitely use a size 16 needle, used for heavy fabrics like Jeans. I would also wash the outdoor fabric in addition to washing the jeans, as it's usually best to use the "wash it all" or "don't wash" theory for quilts, even pet beds. My DSIL has made a number of jeans quilts, using squares of old jeans, especially the pockets, with just a backing of flannel and tying the quilts. I can attest that although they are somewhat heavy, they are indeed very warm and great to snuggle under in cold weather.