@Stephen_Gloor
as mention here http://www.emlid.com/navio-new-hat-compliant-navio-video/
the Ublox m8n receiver is supported by RTKLIB.
Navio+ as well as Reach are based on the Ublox m8n receiver.
Therefore Navio+ and Reach are both supported by RTKLIB.
So technically (in my opinion) there is no reason why you couldn’t use a Navio+ Rover with a Reach Base station connected over an RF Link.
If you like to get a deeper comprehension I suggest to read the the documentation I mention above!