ietrats...
while I have no idea of where your location is, and what city you're talking about....if you've been riding in the city for 10 years and think that your shoulder width is the most relevant in squeezing through cars, then we ride very differently...
mostly the body of cars (down low) and their rear view mirrors ( again, down low) are the determining obstacles for me...if any body part, the width of my hips are most relevant in my experience...
and even whith larger vehicles with protruding mirrors and the like....I find that I am able to move my upper body around (ie...twist my shoulders, or do some boxing stick and move **** with my head) to avoid hitting anything

while you've never hit anything with those bars, I bet you I get through tighter gaps than you...'s all a matter of how you ride
-signed,
uptown