Portrait Sidecar displaying horizontal with letterboxing

[dulapeepss]

I have followed these instructions https://github.com/waydabber/BetterDisplay/wiki/Rotated-Sidecar and I cannot get a portrait display on my iPad that fills the screen. I have tried with rotation locked to both portrait and landscape on the iPad, and with no rotation lock, and none of these options help.

[waydabber]

I see. I'll need a bit more info on what step in particular did not work and/or various screenshots about the setting or what went wrong.