I'm building the Walther's Northern Light and Power structure in N scale and scratch-building a complete interior since all of the windows are so large. (Walthers has an HO interior, but not N) I have one problem with it and need some advice. I have a floor in it, which prevents access from below. I glued this in place, fully expecting to not glue the roof, which I would use to access lighting/bulb changes. The problem is that the roof does not sit well on the molded guides. If I glued it, it would be fine. Without the glue, it pops up slightly, as there's not enough weight to hold it down into proper alignment. So....how do I get the roof to stay in place, but still be removable? Some kind of weight on the bottom side? Weight ON the roof by some clever roof detail? Scratch a new roof that fits better? Not sure which way to go.