Tomorrow I'm going to loosely fit the rear heater, which I removed a while back after it leaked, to have some "before" pictures.
Right now, I am thinking of installing some 6 x 9 speakers in the bulkhead. I got the speakers for free. While this will cut down on room, which is one reason for installing this bulkhead, I don't want to cut any original Westy cabinets for bigger speakers.
In case you are wondering how I will get more (storage) room with a new bulhead, my van is a westfalia weekender and is has a plastic bulkhead that slopes inward (to rear of van) at the bottom. Likely done for a fit more foot room in the back, VW (or Westfalia) envisioned that this was a daily duty van that camps occasionally as opposed the full camper with a straight up and down bulkhead.
I'm on the fence on doing prototypes in basic plywood, or using a nice birch ply, if correct thickness, and just going for it.