Charlie,
You've been patiently waiting to see how your dividers worked out for my rig. I finally got a chance to put them in - worked and fit perfectly.
I took some pictures of the installation that you are welcome to use with your instructions.
I really like that you can slide the dividers out to clean the cupboard or to get at the battery compartment. Great job on the C-channel.
I would only add one thing to your instructions: After marking the center divider, you should probably move it 1/16" towards the back of the cupboard to allow room for the two small dividers to slide in and out easily.
Also, the center divider could have been another 1/8" longer and would still have fit easily (I know you had to err on the short side without being able to measure the piece yourself).
I may replace the countersunk screws with pan head to take out some of the slack.
Great job on the height of the dividers - any higher and they wouldn't come out of the track.
I think you should patent the system and sell it to Camp-Inn for millions!

Seriously, I think this should be a standard option available for every trailer. There's already a Nicole Guard, perhaps this could be call the Charlie Rack.
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Fit all the pieces in, and mark the track for the center divider.
Screw in the C-channel for the center divider.
If you look closely, you can see that I moved it 1/16" back from the pencil line.
Slide the center divider into place.
Slide in the two small dividers and measure across front and back to make sure they are square and parallel.
Mark the track for the two small dividers.
Remove all three dividers and screw in the two small pieces of C-channel.
Slide the 3 dividers back into place and you're good to go. (Great job, Charlie - just send me 10% of your first million).