I've cleaned up some loose ends in the design, and I just now submitted version 2 to the fab. In the end I decided not to change the spacing, because I want to continue using the various radio shields I already made for it. It may not be perfect, but it served well enough the purpose I meant for it, which was having a common platform for comparing different radios. Aside from the hardware design being a bit more polished, from a programming perspective I expect version 2 will work the same as version 1.
After I validate the version 2 boards from the fab, which should arrive in about a week, I'll replace the version 1 files with the version 2 files, at which point I will remove the "work in progress" tag.
The good news is that if you liked version 1, you'll probably like version 2 even better.
In order to properly test it, I should probably start with all new batteries. I did capacity testing on some of the older batteries and then retested their capacity again to see if the numbers matched. They didn't. So, given the small sample size, I'd be weary that there might be too much noise in the sample to draw conclusions if I start with batteries that are already impaired.
What became clear though is that batteries which just sit in a drawer can degrade quite a lot, and that it's not from overuse or re-charging. That's just what happens to NiMH batteries as they age. I guess it shouldn't be surprising, because that's what we expect from alkaline batteries also. But maybe some of the impairment was due to allowing their charge to fall while being stored? That seems to hold true for SLA batteries. Not sure about NiMH batteries.
So, unfortunately, I just don't have the data to say what the effects of trickle charging might be. If it turned out to actually extend the useful life of rechargeable batteries, then that would be an interesting outcome. Maybe someone reading this will feel inspired to conduct such a test and post the results.