I found adjusting the cinch with earpieces in next to impossible. Was able to move the cinch with earpieces out and cable laid flat on a table. Not the ideal situation, but then I also found the cinch doesn't un-adjust while wearing them, which is a good thing, no?
It's pretty thin though yea. I wrapped a wire tie a couple of rounds around the wires for my Delta and it holds well. Might work for the FLC8S cable too, seeing that it's coiled and knobbly-ish.