I like the way you created that holder for your blocks. I use blocks, similar to what you did. Mine are cut out of a support post that came out of an old barn, well over 100 years old now. Solid blocks, will last forever. The original post has chew marks on it in places where cows or horses or sheep chewed on them.
I carry mine (I have 6) in the pass-through. They're pretty heavy, and would like to get them out of the pass through. I started carrying them in the truck (tool box sides) to free up that space in the camper.
Unfortunately, the configuration of my tongue for my Outback does not provide any space to add anything. It's just designed strange with the font cap that curves forward over the tongue, and then slopes back. The battery actually sits under that ledge and the propane tank cover is so close to the front cap, it actually touches.
But, your creativity is now making me think "outside the box" ... literally!
Nice modifications there, TxTwoSome! All of them!