I've microdosed DOC anywhere from 10-30 times?
If you're looking for the expanded creativity and perception of microdosing mushrooms or LSD, it's not really a great substitute. If you're looking for a nervous system uplifting, stimulant-ish microdose, it's pretty good. However, I find it manifests as anxiety pretty easily, just like DOC does at regular doses, if you're not really busy and physically active.
Dosage wise, past 200-300 ug it starts to get too stimulating, distracting, and anxious. I'd recommend 25-150ug? Shit is strong.
Oh, and I just read "below threshold effects". If you're going to try and microdose it where you can't feel anything, good luck, you're going to need to take less than 50ug.
Final edit: I end up regretting microdosing it about half or over half the time I do. That's how easily it can lead to anxiety and general discomfort IME.