Ingenious,....fabric that matches the wall panel to boot so it looks nice. Cut out grate holes where you want them.....wonder where Earhart placed her grills, as in the few photos I have, I can't see them. Some pondering on my part though, how does the fabric tube stay open, in case someone placed an object upon it, either unintentionally, or perhaps a child seated in back of the passenger in front of him, tires of kicking the backrest and decides to stand on the tube, causing a stoppage of heat flow to the passengers behind him/her trying to freeze them out, and in turn giving the passenger in front a concentrated heat blast?
On a more serious note; what continues the connection located between the heat ducts, where the flap actuator brackets and covers are located? In the photo it is hard to tell if there is a pipe connection running through the bracket , but it seems a hole is provided if it is the case. I don't see a tying of the ends of the fabric ducts around a pipe there, it would seem the transfer of heat between ducts might be interrupted if some transition piece wasn't installed there.I noted on the edited attachment that on the aft end of the Starboard duct, something seems sticking out of the duct, or maybe it is just wallboard material. I don't see the temperature of this type of ducting becoming all that hot, with such easy passenger access to it....maybe some 75-80 degrees?
As far as the piece of wood, I wonder why it would be necessary to use it to mount a dado atop, as there are already two multi-ply sheets of wood to attach it too.