We've never done any crown molding before, much less mitering. This is all new to us and we're doing research to learn how to install crown molding that comes together at inside corners. My question is...Why isn't the back side of crown molding made to fill all the way up into the corner where the wall and ceiling meet, filling all the space and leaving no hollow space? This is confusing. We really need for one end to be solid to the corner because it is butting up against an installed shower surround wall. I'm afraid that the gap behind the crown molding will show when it is butted up against the shower surround. What solutions do we have?