The Spanish gun makers seem to build their shotguns using long tang trigger guards. I have an Ugartechea sidelock with a long tang trigger guard. It came from the factory that way, I didn't ask for it as a custom add on.
I believe I read that the AOC/SG Ugartechea boxlock was designed based on best features discussed and agreed to by a group of three shotgun men, specifically, Jon Hollinger, Terry Wieland and Michael McIntosh. As I recall in the write up, it stated that the long tang trigger guard added stability and strength to the wrist of the stock. I'm thinking there must be something more to it than just aesthetics.
See attached picture from the Ugartechea factory showing a rack of their shotguns all having long tang trigger guards.
