Very cool! Not quite the same use I was imagining.
I use 10 round tubes to cram and jam onto my markers so I need access to individual tubes. Three of them fit fine in a single shingle - as one of the images in the post you linked shows - but in my experience they aren't as secure as I would like, and if you use one or two the remaining tubes can lean or slide around in the pouch. A kydex insert in the shingle pouch would retain and space out the tubes for easier individual access.