Colin, If you want to try something like what you're trying to do with a plastic sheet, you make want to try a soft material shower curtin. You could make several smaller pads to fit underneth you or a larger one to cover your half of the bed. I wear cloth diapers at night also, and my diaper leaks occasionally. What I use ia a waterproof crib mattress cover. They won't "crinkle" like the plastic sheet does. It's large enough to cover the side of my bed without bothering my wife. You can find these in the baby section where cribs are sold. Good Luck!