I'm building a 14x16 tiny house and doing a metal roof. It's a slanted/skillion roof and the rafters are running down from the tall end to the lower end on 16" centers with no cross braces. I'm questioning whether I need to add 2x4s in between all of the rafters or not. The OSB won't be a problem because 4' will always break in the middle of a rafter, but I don't think the metal will always break directly on top of the rafters where I need to screw. Is it okay if some of the screws going into the metal just go through the OSB? Will it have adequate holding power? And should I be concerned about leaking? The rubber for the screws should obviously stop leaking but I'm curious if it's normal to do it this way or not.