it's well past the placebo threshold,
Not to split hairs, but come on. You're saying 50 µg is "well past placebo"? If anything, threshold is probably more of a range given how different people respond differently to LSD. I would say this range is 25 µg - 50 µg at its lowest. The range from 1 µg to 24 µg is not reliable discernible from placebo in my opinion, but I'm also willing to admit this is just my best conjecture versus your best conjecture until someone reliable puts out a real study and it's repeated a few times, with human volunteers at that. Think we'll see it in our lifetime though?
Haha, I just need 4 picograms and I'm trippin' fuckin' bollocks, mate!

… I'm just kidding around though, it's probably not that exact of a thing and there may be other factors to consider for where this threshold is, e.g., purity, decomposition, time since last serotonergic drug use, renal pH, age, metabolism, drug use history…
it's meant to be on the edge of placebo
No I think it's meant to be on the edge of actually tripping by staying sub-threshold. It's not represented as a placebo; it's represented as a "sub-threshold microdose".
I wonder if anyone is out there microdosing insulin… or getting their kicks from microbumps of coke. "Just a grain or two every three days and I have so much focus, bruh." I get schwasted from putting beer in a sweet breath vial and then just taking a couple drops under the tongue every other day, you see. What I do is, I dip the tip of a toothpick into a solution of 5,000 parts water to 1 part ketamine, and then I chew on it for exactly 2 minutes every eight months, and I swear, it gives me so much more creativity, lol
so why would it produce a significant and measurable result?
Though it may be subtle, the result should still be measurable or else it's entirely ineffective and a pointless waste of perfectly good drugs. Why would someone keep doing something that doesn't produce any measurable result, then defend the practice as significant and measurably different despite all evidence pointing to the contrary? Not saying this is you, just that: you don't go to the amusement park and ask to take a micro-ride of their best rollercoaster or request that they slow it way down for you because you're going to be doing your taxes while on the ride… because that's what microdosing and half-hits of torn blotter & other scared-to-trip doses are like, to me. Doing taxes while on a slow rollercoaster that never goes any higher than a few meters.
pure MDMB-4en-PINACA that I had on hand, just a single gram, and it became probably 10,000 or so doses? 2,100 tabs and the remainder in vape juice. What the hell am I even supposed to do with this?
Idk, gift it to trusted friends who enjoy it?