You know the stoplights are fucked up as a football bat in this town when the guy in the truck behind you jumps out to go hit the crosswalk light so it will cycle the stoplight.
You can't run a 13.7" pinned and welded and make it to legal length if that's what you're thinking. MAYBE you could if you use an ADCO spacer, but I doubt it.
If I'm not mistaken, there's 1/2" of overlap for the threads. 14.5" barrel is gonna get you so close that it won't be worth it to cut the barrel and rethread it. I think my Surefire is 2.375" also.