To me this is an interesting topic.
H&H London have a number of Try Guns both SxS & O/U in various bore sizes . West London SS & EJ Churchill do also have a number as does Ian Coley at Andoversford , so they are certainly about and made by various makers . But is surprising how few people use them for a purpose made fitting , often preferring to hack wood off or put it on to their usual gun . Strange breed the Shooting Man.