Got it done!
Selected USB charging components on EBay. Next decision was where to mount them. First thought was above the dinette. Unfortunately, the components are too long to fit between the upper and lower skin of the cabinets. So, I decided to put it in the stair well with the other panels.
My advice would be to avoid the 4 component panel and stick with the array of three; a switch; DC voltage meter and USB charger port. Even the switch isn’t necessary as someone calculated how long it would take for the DC volt meter to deplete the batteries when boondocking; I believe he said it would take several weeks.
The wiring is fairly easy; all are daisy chained with positive to positive and negative to negative connections. I’d highly recommend putting it all together and connecting to a 12 volt battery to test the components. If everything works correctly, take a digital photo of the connections before installation. Its much easier to reconstruct the wiring from inside the cabinet when you have a diagram. It would also be much easier to mount the panel higher so the drawer hardware wouldn’t be in the way of the wiring as much.
I tapped into the wiring for the awning switch for power. I realized there is potential for snags and other malfunctions with the exposed wires behind the panel. I fabricated a shroud to protect the wiring using green plastic from a cat litter container. A few minutes with a heat gun, a board for a form and leather gloves to press the plastic into shape; ain’t pretty but gets the job done.