If you can carry and conceal a FSH, then certainly you can carry and conceal a firearm, even a serious piece of steel like a full size 1911.
As I sit here and think about it, I am never in a scenario away from home where I would have my FSH but not have my KAHR K9 or something larger near at hand (except maybe in the exhibition hall at the Blade show, or in a gun show where you must leave your ammo at the door.)
Any self defense scenario I can imagine where you would be justified in using a knife against another person is a scenario where use of a firearm would also be justified, and using the gun would probably be easier to defend in court.
Maybe there are jurisdictions where you can legally carry a FSH but not a firearm, but it's hard to imagine. The FSH is what it is, a superb hard use, multipurpose blade.
The Busse that I most associate with self defense is the original Mean Street.
If my feeble old fart memory is not failing me, when it was introduced, it was marketed as a concealable, thick, brutally strong blade that would not fail when encountering bone, various clothing items, etc. IMO a much more practical defensive carry than any SH.
Hey, I just remembered one scenario where the knife might be equal to the gun. A friend of mine who is a prosecutor once told me of getting on a small elevator in a courthouse and as the doors closed realizing that a huge man whom he had once successfully prosecuted, and had received death threats from, had boarded the elevator behind him. He told of standing there helpless, wondering if the guy was going to suddenly attack him or not. Said it seemed like the longest elevator ride he ever took. Maybe in this situation when there is no way to retreat from close arms length, a knife would be as good as a gun. I don't know.