Thanks for the "write-up"; I may have to try this on my cheap eBay tube doors. Do you have any details on the rubber bumpers?
Also, all-thread might be cheaper/ easier than screws.
Guardian services are separate from the radio subscription.
Also: if you call one service (they have different numbers), they don't seem to know the other exists.
Looks like this one:
https://www.amazon.com/Automotive-Integrated-Electronics-connection-USBCDPLAY2/dp/B07DJ2FBJY/ref=sr_1_3?crid=R9YX3IT7GO2T&dchild=1&keywords=car+usb+cd+player&qid=1591160819&sprefix=car+usb+cd%2Caps%2C309&sr=8-3
This reminds of a friend in high school, who mounted spotlights in his rear window, on a switch (for tailgaters). It didn't go over very well when a state trooper (NJ) came up behind him.
Not everyone has multiple dealership options in their area. My local dealer has been incompetent on several occasions and I won't be returning. The next closest Jeep (Chrysler) dealer is 73 miles away, from my home.