Give up? NEVER!
I think I am going with a "thru the wall" sleeved AC. Not to be confused with a window or wall AC. I don't want to get involved with the plenum requirements of those. It can be mounted at a side location with a single louvered panel to the outside for required airflow...in and out.
Toastie is doing a nice installation of a room AC with a plenum...looks good.
"If it can't be reduced, reused, repaired, rebuilt, refurbished, refinished, resold, recycled or composted
then it should be restricted, redesigned or removed from production."