Hmm. OK. That may be part of my problem. I was going by the instructions
here, which shows removing the hammer before the main spring housing (and reverse order for reassembly would, of course, have the main spring housing going back in before the hammer). That could be part of my problem!
I'll try reinstalling the main spring housing last, after the sear/disconnector, hammer, thumb safety, sear spring, and grip safety are back on.
Getting the main spring housing pin back in is a pain as well. I can't just push it in, since it's fighting that little locking spring in the middle of the main spring housing which "notches" into the middle of the pin. I have to whack on it to get it through. I'm still not sure how best to do that while having to hold the frame and main spring housing against the spring pressure. I need at least 3 hands, possibly 4. I guess I should just stick a small rod or screwdriver into the channel to temporarily hold the main spring housing against the spring pressure to free up my hands to install the pin.
Thanks for the advice, guys. Once I get it back together, then I can find out whether the "fix" worked for my hammer follow problem.