However, it's actually a rather trivial operation to shim up the stationary burr to shift the grind in a finer direction.
Don't get me wrong. If you've got a great espresso machine, don't skimp here: get a Jolly or a Rocky or something like that. But if you were considering a Gaggia, a Baratza, or other low-end espresso grinder, give this a whirl: once modified, it easily compares with that class of grinder.
Step 1: Remove the Stationary Burr.
Step 2: Cut the Shims.
You'll probably need between two and ten shims, depending on your machine. The Supreme Grind isn't as precision-manufactured as some, so your finest grind will be somewhat finer or coarser than that of other machines: you may need more or fewer shims than I did.
Step 3: Fit the Shims to the Machine.
Be sure to both tighten the burr completely (though be very careful not to strip the screw-post threads), and ensure that the shims are not wrinkled or positioned in any way that could cause vertical misalignment of the burrs.
Step 4: Check the Grind.
The burrs should not grind against each other: a sign of poor alignment. If they do, but they didn't touch when the machine was off, you have some wrinkles or inconsistencies in your shims, making the stationary burr higher on one side than the other.
If they're not yet as close together as possible without touching, you can add another shim or two.
Once you've got the grinder shimmed to the point that the finest setting nearly touches the burrs together, you're done. Congratulations. You've just made a decent espresso grinder on the cheap! Of course, it's nowhere near Jolly or Rocky quality, but it'll put up a good front next to a Gaggia or Baratza.