No this rig is a formed sandwich affair. I wanted to miss the beam but went right next to it for use as a ground. I just located it with a hammer and the sound.
I used a hole saw to go through the material. In my case the fiberglass was only about 1/4" think with foam behind that about 1" or so and then the inner wall.
The ring for the inside of a car fender that comes with the antenna worked well for a back support as intended inside. I also had thought I might need to cut a bigger sheet metal piece but it worked fine. That foam was pretty soft looking and I thought tightening the bolts down might crush it but it did not.
You will see that I used that ring to secure the base of the AH-4 too. That point on the tuner is not ground however and they warn you of that.
I used the galvanized pipe strapping for the ground to the frame which you can see coming forward to an existing screw that holds it into the square stock framing around the cab which is ground of course. I have found this stuff works well too with bonding screwdrivers to car bodies in the past.
The pix does not show the eyelets but I used two. I put them into the awning slide area. One about 10' back which gives a nice angle to pull the antenna straight back. I just get the antenna low enough so it will not hit.
The second comes back just shy of the door and I run a small cord from the tip of the antenna through the two eyelets and then down to a small cleat near the door.
This way I can put the antenna up or down without a ladder. My only worry now is just how long that non conductive cord will last. I like to use something light so it does not make the antenna droop when it's up.
The stuff I am using is light and PVC protected but I am not sure about the wear factor at the eyelets. Oh well, it's cheap and I have a roll of it.
I was going to use a 23' marine whip in the same location until it dawned on me that I might get to part under trees from time to time and the length could have been a problem.
With this setup I can operate with the antenna folded a bit or attach additional wire as required for more bands.
Good Luck with your project.