@Ondoid, you’re in good company; and far from the first to be confused by this: “Hardtail” is a misleading misnomer on the part of the manual. The step-stop is a plastic block which swivels to one of only two sides: one of them out of the way of the trem, and another in the way in order to block the trem from pulling
up. From blocked mode, you can tighten the spring via the tension wheel in order to make the trem action stiff enough that strings won’t go flat when you bend adjacent ones. It’s essentially a facsimile of hardtail functionality achieved through cranking the trem against a plastic block. The “T” cutout in the cavity cover plate isn’t like a gear shifter in a car - The reason you can’t move the step-stop into what appears to be a third position is because it isn’t designed to - There
is no third position. So the mechanics of the thing means you can't actually quickly switch from floating trem to hardtail - But you can switch from floating to down-only. And if you want to add something so you can use a finger to quickly switch between the two modes (as one can on the earlier, Ken-era Flys)
VJ has a thread detailing a simple mod.
Here are some photos of my refined Supreme with the rear cover off; so you can see what I'm describing:
Floating (unblocked):
Down-only (blocked):
VJ's 3D model of the part:
BTW, I hope I'm not terribly out of line in sharing that Adrian Belew was under the impression that there was an "up-only" mode on the step-stop that he couldn't figure out. He may still be.
