I had Dennis Stone cut the fork today and dig through his parts bin for some barrel adjusters. I ended up using an FSA compression plug which first sits snugly in the fork tube, then the cap screws down, gently squeezing the headset together. I think it's a better design than the plug the headset came with, which just expands as you screw it down.
The headset that came with the bike came with a plug doesn't have any capability to pull things together -- looks like this, actually, and isn't a two-piece apparatus.
So far I really haven't had any build problems. The drive-side BB was a little tighter than the left, and one of the barrel adjuster was dead-set on not cooperating, but screwed in eventually. Obviously, lots still to do, but in a way I feel the hard stuff is behind me.