“making flats on the galvanized pipe, but only on one side”
Is that like a flat tire that in only flat on the bottom?
I used black pipe. With a build like this, and so much tension on the pipes, black paint ends up covering the wheels. It didn’t seem to matter that much, but somehow it does not seem like a good thing. I never did sand it off the rails. But even with galvanized, it might be a good idea to sand a smooth track for the bearings.
Steve