Hey, "older, no-name" stuff on a single-speed is the only way to go! Plus, the drop-out modification is really spiffy, and I applaud your ingenuity (Especially the part about hanging the bike by the rear wheel to tighten the axle bolts).

My gearing is 18X42 (I've heard that two to one is the optimum set-up, but for the kind of riding I'm doing - easy trails, city streets, alleys, dirt roads, etc - my combination seems to be fine).

It's hard to believe, but I find I'm getting more comments/questions about the single-speed than any of my other bikes (Especially at the local coffee shop), and I've got some zooty road, mountain, and 'cross bikes!?

You mentioned you're using a bmx freewheel w/spacers, so do you have a bmx hub or is the bmx freewheel screwed onto an older style mountain hub and the spacers are being used to get a good chain line (Does what I just wrote make any sense?)?