Totally understand the dilemma, had the same situation in our previous house! Validating to know that as low as possible can help in this scenario. I’ve built diffusers so far, placed on the first reflection point of the left wall and behind on the back wall. Big improvement. Looking to build another one for the right wall. Have now Gik corner trap as well. Cheap treatment elsewhere on the walls overall, but need to replace it with better quality panels. Trying to find the balance without over-stuffing the room.
Very nice, I should consider a local wood worker. Outside of pocket hole screws and wood glue, I’m not much of a builder!