Now, ampr-ripd does identify this host as directly connected, which appears to be the expected behaviour with the new version. All well and good from the Pi, but there is one significant implication - the source IP is no longer my 44 net IP, but it's the public IP of my router, and the internal IP is the 10.x IP of the Pi (my regular IP range. I think that's where things are breaking.
Ah yes, it would be better when ampr-ripd added a "src" option with the IP of the tunnel interface to the /32 routes it adds to the table...
Rob