That's kind of a pain in the ass isn't it? Unless your shotgun is a safe queen, you would be stripping out the set screws or marring up the hell out of your capture points with those set screws.
Is this a legal configuration? As I understand to extend the magazine 3 American made parts need to be changed and a magazine extension does not count as 1 unless it is a 1 piece to be 922r compliant. Correct me if I am mistaken.