It sounds like you got a better part, I had to glue my gasket as it was not vulcanized. I would say that the 1/2 thick part and size to the pot metal frame sounds right. I used a paint marker to locate where to punch the holes.

Paul

1941 Chevy 1 1/2-ton WW2 4x4 dump truck
In the Stovebolt Gallery
Lots more pictures