I own the same bag as Karen--the Think Tank Commuter. The 500 takes up one side of the bag.I love my ThinkTank Commuter bag. The 500 sits on one side and additional lens and/or bodies go on the other side. Space isn't the problem for me....it is weight. I could easily put more weight in the bag, but would not be able to carry it easily. I try to keep the bag to about 20-23 lbs. The TT Commuter easily fits in the overhead of small regional jets like the Embraer RJ 145.
I also carry on board a large computer bag with my computer, chargers, card reader, 1 external HD, USB hub, AND another camera body and lens. The computer bag usually weighs about 15 lbs. The computer bag goes under the seat in front of me.
I wear my photo vest when traveling. Not very fashionable but very, very functional. Batteries, CF/SC/XQD cards, a second external HD, meds, wallet, etc go in the photo vest.
Tripod/monopod/gimbal/heads in checked luggage.
This worked really well on our recent trip to Costa Rica and previous trips to Kenya, etc.
that is pretty cool, I sometimes use something similar, a lowepro backpack in a standard carryon roller bagRandy I showed you this at Bosque a couple of years ago, I use a Lowepro Proroller 200, where you can take the inner bag out and it becomes a backpack that can handle a 600, with hood, 2 bodies and a 80-400 type of lens and tc's as well. Pro Roller x200 AW
And yes the inner backpack fits in regional jets over head bin! With a 600 in it!
I have no idea why this bag isn't at the top of the list for all travelling Nature & Birder photographers, its a great bag, very intelligent construction