thanks for the suggestion, Trunks.
when I first made the prototype, the pin was long enough to accommodate an o-ring. folks wanted me to lower the profile of the mechanism there, tho. So I made everything as short and low as I could, while still allowing for decent function. This made the protrusion of the pin/post short enough that an o-ring interferes with function. . . . So, not really, . . . not when I try it. →As the post is (and needs to be) free to travel ↑↓ a bit, the o-ring would get pushed/rolled up a hair in this motion/dynamic, and would either roll off the end of the pin or booger up the gap/contaction.
The solution is simple, however, and not a new or ingenious one. It's the dynamics of it that are mildly surprising and pleasant. If I make a shallow countersink in the top, just enough to "house" the o-ring flush with the top, and I make that countersink of appropriate shape and dim, it holds the o-ring at that height, allowing the post to slide up and down without the o-ring being disturbed. Also, it allows for easy motion when the pin needs to move; but no motion just due to gravity. So, it just so happens that, with the right o-ring, and the right countersink depth and diam., it works better than would be expected. As I'd mentioned, X-puppy had proposed something like this, and/but it didn't seem sufficiently necessary with the Pinch to merit the added part, shape and fiddling.
The switch needs to be out of the way, tho, to install the o-ring and pin. So, that's the mildly awkward. But, once in place, it acts like it will stay indefinitely (or until
cleaning is necessary).
I ended up taking some pics of the successful version in a scrapwood test block. .. .
. .. was it good for you too? 
