There are all sorts of TABs. The majority fasten to the seatpost. These have a tendency not to follow the tandem 100%, so besure to take a bit wider corners so the TAB does not hit curb or falls off paved road edge.
The only TAB that we know of that follows tandem 100% is the Burley Piccolo with its Moose rack hitch as mentioned and pictured above by R900.