How I read it in the book for making the Evening Star was that the copper studs were made with and incomplete thread that would seal itself into the backhead.
I have visions of the threaded portion breaking off and you are left with just the mount part.
Even then I cannot see this method being a problem as the pressure on an 8Ba pin is very small and we all know that the worker is an expert and tried it out on a bit of spare copper?
I think I would have followed the method myself but if I was having a commercial boiler then I would specify mounts anyway but I dont have £1300 plus for a boiler, this was the last quote, previous to the legislation it was £320!
I know all about traceabilty and quality control and could show severe failures of prime equipment that my son has to endure on his deep sea survey boats.
Clive