Meanwhile, bike.5 is still coming on nicely. I've added a centerstand; when I'm out caching, I stop every few hundred yards, and the problem with a sidestand is that the ground is often too soft, or too uneven. I think a centerstand will work much better.
And I've had an idea. I don't have to run this at 24 volts.
My "24 volt" battery packs are actually 8S of Lipo made from two 4S packs; nominally 28.8 volts, actually 33.6 when freshly charged. If I went to three 4S packs, that would be nominally 43.2 volts, 50 when freshly charged. And that's a lot to put through a 24 volt motor and 24 volt controller.
It occurred to me that I could get a 2S pack, and run that in series with two 4S packs to give me 10s. That would be 37 volts nominal, 42 volts freshly charged, and I think the 24 volt motor would be OK with that. But the 24 volt controller probably wouldn't, so I've also ordered a 36 volt brushed controller. If this all works, then bike.5 will probably have the pep that it's lacking right now.
So there's lots going on, down in the bike shed.