One of the little mysteries of auto history is the soft spot in roofs. Metal shaping technology wasn’t up to the task of pressing out a complete rooftop without wrinkling and stretching the middle. GM finally perfected the ‘deep-draw press’ in 1935, and others soon copied.
I’ve been puzzled by the continued use of crude and unmaintainable wood frames covered with cloth to fill the space. This continued from 1920 to 1935 in most cars. There was no technical reason why the space couldn’t have been filled with a single-curve piece of metal, welded or gasketed in. This would have been a much more durable solution, but it wasn’t even tried until 1936 by Chrysler and Hudson as a (ahem) stopgap until they could copy GM’s press tech.
I’ve also been puzzled by the failure to use the hole as a sunroof. The Euro divisions of US companies filled the hole with a folding or sliding sunroof, making lemonade from the soft lemon. This design was obviously available to Detroit, but they never tried it.
Even more puzzling: In 1939, after everyone had the new presses, actual sunroofs appeared for the first time in some US cars. The hole was no longer innately there, so it had to be cut out specifically to form the sunroof.
Did anyone buy and use those few ’39 sunroofs?
Yes. A 1940 station album from KFEL in Denver shows how:
This is a ’39 GM car, probably a Buick. They’re using the sunroof as a ‘camera port’.