when I was at the Rodefer Gleason auction in 1984, they had an iron mold to make a 48" diameter sphere in thier archives. You could literally stand inside of it.
You are so right on about the SW debacle. Some of the molds went to Davis Lynch who also used to make a lot of rather large pieces. I had a few large molds like the GE street light mold that I sold to Gary Guydosh and not sure what happened to all of those after he passed away. He bought an entire truck load from me when I moved from middle Tennessee.
Somewhere I have a video of an old film from one of the window glass companies showing them blowing the cylinders and then cutting them and running them thru the oven to flatten them. I also have on that same video a film of them making the drawn cylinders that would be up to about 16" long. It's an amazing thing to watch as most in our generation have never experienced it.