Compliant ride and 28 mm tire on a tandem seems a bit contradictory. I must be missing something here!
We are working through a stash of 700 x 37 Panaracer T-Serv that measure 39 mm on our rims. Go fast, ride great, last a long time! When the panniers go on, we switch to 42 or 47--Schwalbe Mondial, Supreme or Dureme or Conti Top Contact 2.
"If you think I'm going to ride tandem with you on a bike with those skinny tires, You are sleeping in your bike cave from now on" sez the woman with the 33 mm tires on her fast race single.
Mount up the biggest QUALITY tire you can get between the stays and try to stop smiling-