Well, I measured the 3s bottom bracket spindle. It's 124.5mm, not 121.5 like Sheldon Brown's database says it should be. What's up with that?

My UN55 BB has a lip on the NDS cup, preventing it from threading in far enough. I got one without a lip. After taking some measurements of chainline, I found that the crank will be centered and the chainline correct with 3mm of spacers.