Don-

My mat is the inexpensive solution to the Jobo mat. As far as I can tell, it works just as well, with the film in contact with the slightly textured but bumpless sheet of vinyl. The results will be proven when I've had a chance to print something from it. I didn't need plastic snaps to hold the film in place- just some bits of scrap vinyl and some vinyl epoxy to hold them down. I purposefully left the mat small enough that it would have an open side (inserted in the drum, it forms a U rather than an O), to make sure the chemistry doesn't get trapped behind the mat when poured into the drum.