Agreed! It's been a while since I had to do something similar with half exposed round timber trusses...thanks.
As for the multiheight first story...I set the open area to 13' ceiling height. Then built a second floor only over the lowered (8' ceiling) area. I've not bothered about the windows crossing between these areas yet, and with the open ceiling I've had to turn the interior attic walls to invisible so the exterior attic gable walls remain on. Much more effective than two complete stories so far.