That's a good idea! I bought a long because it was on sale and got some extra material (I'm 5-11) and we had enough room in the foot box, but why not be really comfortable and have plenty of room? I did ask my wife if she thought the drafts were a problem and she said she had tucked the edge of the bag underneath her and felt zero drafts. For now, we're good to go. You could take an old sheet or blanket, cut it into the quilt size, construct a foot box with duct tape and see what works for you and how much you need the extra. We set up our pads and tried the one bag at home before bringing it on the trail.