I haven't done it, because I usually want the same height all the time. Though, recently I played at a place where there's usually a short barstool, only it was MIA and I had to use a normal barstool, which was too high, and I'd have liked to make a quick adjustment. So, I might do this mod. (The shorty barstool did turn up before the show, thankfully. And normally I have my own stool but at this regular place I don't bother because, there's one there ... maybe!)
I'd use something like this, but hope to find a shorter one: https://formufit.com/products/formufit-small-diameter-pvc-quick-release-pin-4-pack
Also, I'd drill holes in the bottom of the stand's legs. I just noticed that these bolts don't go through holes, they sit in a groove, meaning that if not tightened, the feet could fall out when carried.
Another thing about the 18880 that I learned: If you only need 2 tiers (base and one additional), consider getting the 18882 (mid-level tier) rather than the 18881 (top level tier.) The reason (for me) is that I like the tube openings at the back for various purposes. Currently I made little wooden speaker stands that pop in there for small monitors. Great at home, not quite loud enough for a typical too-loud stage. (I wish I could find some small powered speakers with say 110 dB SPL but so far no luck, and I have bigger fish to fry.) And above, I see a mic stand attached, which would be great too. Or possibly, a music rest. It's just a real handy way to add stuff to your rig.