Turns out the piston cap seals I bought are too tight. Not only do they cost too much, but they have too much friction.
I have been distracted lately and haven't done much work. I need to get bags that are made of different materials. I have been in contact with 2 plastic suppliers that promised sending me Nylon and Teflon bags, but neither of them came through.
I will be sending out requests for quotes to more suppliers for 3" wide, 6" long plastic bags made from tougher material then polyethylene.