Feeling more than a little foolish about the trash bag in the shop vac, I took another shot at the concept. I imagined that if I had a bag with a little more [m]ass, the suction would not pull the sides into the filter so easily. I though about just adding some ballast to the bag, but this seemed a little like admitting defeat. When working on a new foot stool for my niece, I remembered that I had replaced the filter-bag on my dust collector with a less permeable one. I had kept the original bag and it fit nice and snug into the shop vac canister. I added a pair of my daughters tights to the filter for extra filter life and the system does work well after much more extensive testing. So, I can now recommend this approach.