There is a way to bring all your guns into the tops. Even someone with 5 speech skill can do it. Just Talk to Swank. That's it, and after this the tops greeter will never take away your guns when you enter the building.
BTW: 10mm pistol loaded with JHP ammo is better than this work of useless art. Hell,I'll pick my old moded 9mm pistol over this thing.
I did that on my first playthrough, yeah. I haven't even found the silencer for the 10mm this time around, but I haven't been to see Benny either, on this playthrough.
I wish you could mod the Unique weapons, though. A 9mm Maria with scope and silencer would be nice.