Shop Vac Redoux

Update:  Plastic bag in shop vac = bad idea.  I don't know what I was thinking--I knew that the plastic bag would get sucked around the filter and cause the vac to have no suction--similar to the water intake on an outdrive.  I have a heavy canvas bag that will fit into the canister--going to try that.  Maybe an internally expanding ring of some sort to keep the bag away from the filter, hmmm.....Maybe an MDF disk cut the ID of the canister that stays in the bag...