I have electric power supply and other connections figured out for putting a wireless CarPlay/Android Auto receiver in place of the factory navigation system display in my 2004 Mazda RX-8. Now I need to figure out how to keep everything physically in place. Normally I would turn to 3D printing to solve such problems, but this will be on top of a black car dashboard. I know for sure 3D printed PLA plastic parts soften and deform under summer sun, and that wasn't even inside a car. I think PETG could withstand such temperatures, but I'm not sure.

Uncertain of plastic durability, I turned to metal. This was the folded sheet metal tray from a Seagate external backup drive. I cut out the four tabs that formerly held screws securing the 3.5" HDD in place.

These tabs were then used to hold the receiver in place, using original support posts and their screws. This is not a very precise mechanism. Because the tabs would shift slightly as I tightened the screws, it was hard to keep the receiver in exactly the right place to ensure the screen image is perfectly centered. After several attempts ended with a slightly off-center alignment, I decided "meh, close enough" and moved on.

The slight misalignment made me glad I decided against drilling a hole for the integrated microphone. I haven't used voice assistant features and I don't intend to start. And since I didn't drill a microphone hole, I don't have to worry about precisely aligning it, either.

Now I need to put the original display circuit board back in, without the display. The only reason it is still here is because it also handles retraction motor control and I wanted to preserve that capability. I first tried to fit the circuit board while it was still installed on its metal backing plate. I liked the extra structural rigidity, and I hoped the metal plate would act as shielding protecting the receiver from interference.

Unfortunately, there's not enough room. Top edge of the circuit board sticks out beyond where the lid would go. For everything to fit, I will have to go without that metal plate.

The receiver's own plastic enclosure should act as electrical insulation on the bottom. On top, I cut down a depleted Costco shop card to act as shield and insulation against the retraction servo assembly.

A quick in-car test looks good enough to proceed: the retraction motor worked as long as I ensured it stayed in operating range, and the receiver boots up as expected.

With that success, I buttoned everything down. The original LCD circuit board, now just a retraction motor control board, is then secured via zip-ties. Then everything was put back in the car for a full-up functional test.