Harry,
In my opinion it is much more difficult to cut the scallops in the metal than in the wood. It does take a bit more time in stocking but with the draw-bolt pulling the butt onto the action, it goes fairly simply. That said, I have probably files my last scallops in anything but a very plain boxlock. they don't enhance a borchardt, or most any single shot IMO.

Now the forend is a bit different and given the way I bed a single shot forend, less than advantageous.
(BTW: who are you, LRF?)