Pjs When I made the cylinder I used a 4" rod the piston was 8" the wall thickness on the cylinder was 3/4" and yes double acting the main problem in making the cylinder was I had to make such a short head or gland and a thin steel piston of only 1.5" the head was only 2 inches thick and made of steel as well os I had to use a bronze bearing in it the power unit was basically like you would find on a larger log splitter or pony unit on a hydraulic operated trailer. so it had a 4 way valve you just moved the leaver left right or center. the hosed were only about 25 feet so we just lowered everything from floor to floor as we went down. Simple fast and very efficient Hung from a chain hoist on a tripod. I imagine the company called Concrete cutters probably still has it leaning against a wall in their shop I can't imagine them ever getting rid of it.