I just connected on my '12 Mac Mini server and it was surprisingly easy to set up.
I have a 3TB Time Capsule
2012 Mac Mini
1 Line connected from Mini Ethernet to TC
1 Line connected from Thunderbolt - Ethernet Adaptor to TC
Open System Prefs
Go to Network
Click the sprocket/drop down menu and choose Manage Virtual Interfaces
Click + to add a new Link Agrregate
Name the Bond and choose to bon the ethernet and TB adaptor
Within seconds the new bond showed in the network devices list and was working.
I have not conducted any "speed" tests as of yet but should have something up soon.