We recently installed 2 Becker vacuum pumps on a 20' table. They combine at the pumps to a singe 1 1/2" line that runs to the table and is about 75' long. We seam to be having some trouble holding material down to the table through the MDF. The meters on each pump are reading around 16 oz of mercury which doesn't seem to low but was wondering if anyone had any solutions to help with hold down or with getting more pressure from the vacuum's. Also wondering if the air line is sufficient at 1 1/2".