I had the same problem with the expander that VB provided an a similar but longer one. I then bought the SL7 replica expander and tightened it to 8nm using carbon paste. Now it is fixed, no play at all after 1000km with bad roads and some cobblestones. I would suggest to try this route, because you were able to build it without play at first. Not to mention that a micro spacer with head set play might eat up the fork very fast.

Why the SL7 clone? What's the functional difference between a SL7 clone (-+25usd) and a cheap, long expander like this one (3usd, 90mm long)