This is on it's side and would be vertical when mounted
Photos aren't great, so I'll add some narrative. I cut a piece of aluminum plate to fit inside the plastic ammo box to add strength then thru bolted the box to the 1" aluminum square tubes. The funky wooded pieces are temporary fillers so I could tighten the PVC connectors onto the PVC threaded piece coming thru the box. Just haven't gotten around to replacing them yet. The were needed so I could get the PVC connector nice and tight
The aluminum tubing is then thru bolted onto the FWC jack brackets. These are the bolts which would go thru the aluminum tubing
I decided not to use threaded connectors to connect the two 5ft section of PVC to ease dismantling. I just drilled a couple of pilot holes and screws sheet metal screws to secure the push on PVC connectors.
I used it all summer in Colorado driving on some pretty nasty roads. It held up well no signs of wear or discoloration on the rod or reel.
The tubes are lined with foam pipe insulation and I placed a wooden shelve in the box so that the reels lie flat on the shelf. This does serves two purposes. The reels aren't swinging back and forth plus I can carry both my 5 wt and 8wt rods and reels and reels fully assembled. I did need to notch the foam a little at the box end to allow for the larger line guide need the reel end of the rod.
There is a padlock on the box but I wouldn't leave my rods in the holder overnight in a motel, but for a quick run in to a store, bar for a beer or camping I feel safe. also I like the fact that even when I'm camped next to the river, the holder is a safe place to store the rod in camp and not step on it or slam a door on it.