I'm a little late to the party and off back to the topic of crossover placement, but here goes. I know I may get some flack for this but I always put mine inside the door with a piece of 3m emblem tape on each edge that will touch the door(most crossovers are flat and most doors are curved), just make sure you don't have leaky doors. It's how I was taught and it's how I continue to do it. Installation is simple, and they are hidden.