Rob,
There is a thread on this site, under the heading "The .450 #2 passes the test with flying colours" which I started last year. It has a bunch of photos of a double rifle which I just completed about a month ago, in that calibre. Unfortunately I couldn't get the photos to open when I did a search a few minutes ago, otherwise you'd be able to see what a tight, virtually invisible, seam you are able to achieve with the method that I described.