I recently picked up a Mamiya RB67 pro SD along with a whole host of other backs (some Pro S and Pro backs), but there's one wrinkle: The Pro SD back adaptor's revolving action is fairly stiff, and I have to put a lot of power into turning it to get it to turn it into vertical orientation. I originally thought to get some lubricant, like the kind they use for power tools, but I've been told that at no point should liquid be going anywhere near the camera if possible. Is there any way to loosen the back so that it revolves more smoothly? Also, how good is the weather sealing on the RBs? I am considering taking it to the beach but am worried about sand getting into the camera.