My first recommendation is to not do anything that would invite authorities to make contact with you in the first place. "Flying under the radar" really isn't that hard.
If it were me and contact was made, I would only advise I was armed if there was a chance they'd find out anyway. Like, say, if I had to reach back for my wallet and doing so would have a chance to expose a concealed weapon. Otherwise I wouldn't. But that's just me.
Like I posted before, I always ask even though I assume they are armed.