use series 2 2.4
no problem with any radio I am using now. setup the radio test it with terminal window on both xbee type text in both window should apare on opposing terminal window using a PC or MAC.
radios are one time setup nothing to do on the FC side at all!
If you need longer range and mesh support you can take a look at jDrones long-range telemetry. You can upload mesh software on these modems and it works 101% on them. Why?? Well Seppo/RFD who made these modems also helped to develop mesh software that we are talking in here.
We also have custom pixhawk cables for the modems if you need.