Reuasabes work well, but you to remember that on a bed, aany fluid is going to flow toward the lowest point and then move outward as that area is saturated. For that reason, definitely get a large size. If you're worried about the pad slipping around, look at the reusable kind. I have a couple, and they stay in place pretty well. The waterproofing is much stiffer on the underside and has a texture to it that keeps it from moving around (for the most part). If you toss and turn, the pad is moving regardless, something also ameliorated but not eliminated by a larger pad. If it really becomes an issue, you can glue a piece of friction material to the underside. This material is what you find on the edges of tile stairways in many schools, hospitals, public building, etc. It is black and has a rubberized quality with a rough texture, as though sand paper was covered in liquid rubber. You can buy this stuff in any hardware store. It can get wet, but I'd try a sample before putting in the dryer on a medium or high temperature. But reusable pads are relatively thin, so they air dry very quickly. Just don't wash them in hot water.
