Originally posted by mattt I then switched up to a Large Tenba Messenger
I have a Tamrac messenger style - its a medium size bag with a few simple modifications.
It can carry a tablet or netbook (personal travel), but my fully equipped 14" notebook (business travel) gets a bit snug. But the notebook only has to be in the bag during the flight part of the journey.
I found a second slim PC messenger style bag of the same general color/material as my photo bag. I removed the shoulder strap and use double-end snap rings (look in pet supplies) to attach the two bags back to back at the D rings. Nobody has stopped me claiming I am carrying two personal bags on to the plane - it looks a lot like one of the doubled security-friendly notebook bags.
At the hotel, I can ditch the PC part of the setup. I don't need as big a bag for field photography. And then I have a waist belt for the photo messenger bag. I wear both the shoulder strap and the waist belt to distribute the weight, and the waist belt keeps the bag from swinging and smacking into things when I walk and bend to take photos. The waist belt slides around me, but in transit allows the bag to mostly stay put either behind my hip, at my side, or in front of my thigh.