Yeah, I am a bit ashamed to say I did just lay it in there. The insulation and its connection to the door panel were (are so far) strong enough to keep it in place. I also have not had any rattles. If I were to re-do it in the future for any reason (e.g. I see the insulation starting to give, I hear rattles, etc), the way I would attach it is industrial velcro. I've held 10 pound electronics in place inside electrical panels, garage door opener on my sportbike, and a ton of other stuff that is rock solid with that stuff. You can go to Home Depot and get it in the hardware department. The panel is flat, so I'd probably stick a 3" wide, but 4" long piece on the door, and then on the bottom, obviously, of the crossover.
I just left the factory wire for the tweeter in place. It seemed to be just fine and not too practical to remove. I attached it to the other wiring nearby to reduce any liklihood of hearing it rattle, or having it possibly migrate to an undesired location. I used a wire tie to secure it.
The wiring itself, I snipped the wire coming into the mid-driver, soldered some 16/2 wire onto it. Ran that over to the crossover. Then, ran 16/2 back through the door (using the channel already there on the inside of the door panel) up to the tweeter pod. The other 16/2 runs back into the door (taped to the input 16/2) for connection to the Hertz mid-driver.
Both my rides will smoke ya
2010 L99 2SS/RS - Hertz HE HSK 165 components/PPI A404 & A600/JL Audio 10W6/Audio Control EQX, FAST Intake Manifold