Hi 3800,
Welcome to the Heartland Owners Forum.
On our 2011 Landmark, the factory installed bedroom A/C unit is not tied into the ducts for the living room A/C unit. I believe Heartland worked with Dometic to redesign the ductwork and A/C units a few years after ours, calling it Whisper Quiet. After that, some other models moved to a similar design called Cir-q-lair.
On those units, the ducts on one side of the coach are for outflow and the ducts on the others side are air returns. I'd expect your 2011 doesn't have this duct design.
So I think you'd have 2 problems: First, the ducts in the bedroom are probably in the wrong place to tie into. Second, the airflow design would probably not work as well as on a unit where the ducts have been designed for multiple A/C units.
I'm pretty sure you'll end up with a non-ducted bedroom unit, just like everyone else with a 2011 coach.