I've been reading about a sew in interfacing called Stiff Stuff here on the Board. I haven't tried it yet but from what I've read people really like it for bags and other things. I was going to try it in place mats. If you google it you will find numerous references to it but make sure it is the interfacing as stiff stuff is a name of something used in crafting. From what I gathered it was not thick but rather stiff.