Ok, here's how you set it up (on a Mac):
Mastermind MIDI Out -> MIDI In 1 on interface
Mastermind MIDI In -> MIDI Out 1 on interface
MIDI Out 2 on interface -> Axe-Fx MIDI In
MIDI In 2 on interface -> Axe-Fx MIDI Out
You can still use a phantom power box if you want - just connect the above "Mastermind" connections to the box and the box to MIDI Out as usual.
Install and run MIDI Patchbay:
Set up a patch from MIDI In 1 to MIDI Out 2 and MIDI In 2 to MIDI Out 1. This allows bidirectional communication to pass through the interface.
Install and run MIDI Monitor:
www.snoize.com
Then, edit a preset name and capture the communication as you do a Get Preset Names. You might want to turn off the Axe-Fx ports in MIDI Monitor so you don't see communication between Axe-Fx and Axe-Edit, and turn off everything in "Spy on Output to Destinations" so you don't get duplicate messages. You can also turn off MIDI Clock in the Filter section if you're seeing a lot of clock messages.
Thanks for giving this a shot! Please let me know if you have any questions.