Honestly, because of the way BiaB is formatted to appear on the screen, I don't see why running in portrait mode should be a problem. Regarding your comment that BiaB takes on the dimensions of Monitor #1, yep, I have the same problem. If I want to run it on my smaller screen, I un-maximize it then resize BiaB's "window" such that it fits on my smaller screen. Unfortunately, when I maximize it again, it reverts back to its size for the large monitor.