It turns out the rear axle on my Formula hub wasn't quite long enough for the wide spacing. Once I put the spacers on, I could just barely get the nuts to start threading on. After much searching and buying one incompatible axle, I'm now waiting for the right one to come in the mail. It appears that Harris Cyclery is the only place in the world you can get the thing.
The rainy weather has helped me be patient to a certain extent, but today I decided to throw my CX wheels on there with spacers, just to have a complete, ridable build.
With the fixed gear wheels and the too-short axle, it weighed in at 21 pounds, 0.5 ounces.