So, I upgraded now to running at 300kbps as the default, and all is good.
Not surprisingly, RSSI is a lot lower than with a narrower bandwidth. What did surprise me, though, is that RSSI seems to fall at a much lower rate with distance.
Not sure why that is, but I'm glad for it.
[Edit: Doh! Of course, because it's a logarithmic scale, not a linear one.
]