For anyone who wants to try the B Pillar location: the proximity antennas WILL fit, but you have to trim off the mounting tabs.
I just put them in my vise and used a mini-hacksaw to cut off the tabs- I was going to use 3M tape in the door panel anyway, so if they didn't fit, there'd be no problem.
So I placed it in the driver's side B-Pillar "channel"...and it fits just fine- the channel is deep enough that there doesn't seem to be any interference when the trim panel is reinstalled.
One bonus: much shorter wiring is needed to run to this point. Alas, I did NOT measure this out, but you could safely go with half of Jimmy07's length cited in the opening couple of posts- and you can also pin the antenna connector in your house, not in the vehicle. BTW: trying to get a pic while holding the seatbelt out of the way when one hand is bleeding (cut my finger) is a PITA! So no "depth" view...at least not of the driver side antenna!
EDIT: I got the pin remnant out of the connector and did the Passenger side antenna (same as the driver). I took a pic of what it looks like when stuck on there; essentially it's a pic of the b-pillar from the inside of the back door looking forward (on the passenger side of the truck. As I said, even with the connector in place, there's not a lot of projection into the void behind the cover. Now all four antennas show as "Present" when I scan the RF Hub System Status.
Oh: and though I earlier posted the factory location for the front antenna (mounted to the ORC module's bracket), if you want to install it there, you'll have to fully remove the center console to get at the ORC. That bracket can't be reached by only pulling out the center bin/cupholders, and I'm not sure where the console is connected up front, but it wasn't moving for me. There are a couple holes in the console base so you can SEE the bracket, but unless you have 3" wide hands, the largest of the holes is still far too small to reach in. So I used more 3M tape and mounted it to the vent pipe that feeds the rear vents on my console. And everywhere I used 3M tape, I also used 3M Adhesion Promoter (B-Pillar, back wall for the Rear antenna, vent tube and the back sides of each antenna).
