Mark,
I'd agree with skooterg; it may be the minority that does carry while on the bike; I think there have been a couple of polls or threads about that at some point. I have a CPL now (again rather - had one in VA years ago & let it expire).
I've had mixed thoughts of carrying on the FJR (FJR content, check). I have two thoughts. Solo, I feel I can take, talk my way out of, (or give) an a can of whoopass as needed. Someone pulls a weapon on you first, then trying to out-draw them is not going to be the first course of action that comes to mind (but shame on me for letting them get the drop). But that all changes with Annette being along. I will not take a chance on whether or not I am able to defend in a worst case scenario.
Whether or not it involves the FJR, carrying a handgun is about what you are comfortable,confident, and capable of using. It's a very touch / feel sort of thing. Give me an M16A4 and M9 and my confidence is rock solid that I can locate, close with, and destroy the enemy. Civilian life is much more complicated though, but have a G17 that has provided may years of reliable service. It will get some relief as I transition to the subcompact G26 for everyday carry (on the bike or in the truck).
Hope this has enough FJR content to be supportive and useful.
oh, and if I were going to mount a machinegun to the FJR, I think I'd drop down to a M240G - 7.62mm with night optic & laser sight. Less recoil than the M2 .50 Cal, which would mean less stress and wear on both the fork bushings and rear tire. Another viable option is the M249 SAW - a 5.56mm automatic weapon - higher rate of fire, and more ammo per pound. But you're giving up the range that the M2 offers. Decisions, Decisions...
Wayne