The cupola has two major parts- the inner part that forms the base and the outer part that ends up as the outside of the cupola. You fit the periscopes, then glue the outer to the inner.
I decided to mount the periscopes then paint the interior the standard "buff" color. To keep everything square I used some temporary brass pins to hold it together. I also ditched the resin portion of the hatch that acts as the hinge rod. I replaced it with aluminum rod for durability and added a matching sleeve in the cupola. The pain the back was fitting the MG ring. Heat is your friend here. I spent a lot of time lining things up- figuring how to mount all this to a wood base and pinning the figure to fit nicely so it doesn't pop out of the turret.
Crap, this is a lot of stuff to write about this. Most I've written in a while. Here are a couple of photos.