By way of explanation; I really want a nice interior (automotive quality) generally and overhead particularly. Looking at what was available ready to install did not do much for me. The product(s) are expensive, have features that I do not want and lack other features I do want.
I plan on making a plug, then mold, then vacuum bagging the final product. If it works out as well as expected. I will have a mold to make more if someone else wants one.
The features I want are, 1) flat areas to locate vents and lights without features that drive the locations. 2) A switch panel angled for easy reading at the front. 3) Recessed hidden indirect lighting along each side. 4) Overhead lighting for the baggage compartment. 5) Provission for air flow independent of the wire runs.
So below are photos of the plug development. It is built up with fitted pieces joined by 5 min epoxy. I then shape using a variety of angle grinder with rough sanding disk for roughing, orbital sander for smoothing and flattening, and hand sanding blocks of various shapes for fine shaping.
I put the canopy cover back on the fuselage to see how the overhead would fit, and work ergonimically. The front switch area was too large impacting head room and not angled enough to easily see the switches. So I cut it down and angled it more. On the good side the front face of the forward switch area is situated perfectly to mount instrument lights. I also decided to keep the overall shape clean and simple.