Hi Danny,
the APs are removed from the v10 DB as the AP model is not recognized.
That will also remove the AP26xx from the v9 controller if they are foreign.
There is no redundancy during the AP replacement.
Personally I'd remove availability during the replacment and turn it on as soon as the 2nd controller is on v10.
PS: don't use 10.41
Cheers,
Ron