Single acting and double acting hydraulics..?

So I am building a little farm project, i have access to a few old hydraulic rams, but they are all double acting, can I make a double acting cylinder single acting by just blocking off one port? Or does it air lock or anything?



Next question, i always see the single acting cylinder is smaller when paired up with a double acting, for example a header reel. The double acting cylinder is fatter then the single acting cylinder, is there a reason for this? Or is this just inherent to the cylinder design?



Thanks.

Single acting and double acting hydraulics..?