The Kata BP502 seems like a good bag for my PD170 plus. I am concerned that it may not meet the requirements for carry on luggage. I've combed the internet for an answer and found zipp. Has anybody had the pleasure of taking their camera overseas in a Kata BP502 and if not, can anyone recommend a medium sized camera backpack that meets the restriction guidelines. Thanks a lot, I really enjoy this amazing resource.

Go to your airline's website and look around. They should post their carryon baggage policy there. For example, here's American Airlines policy:

http://www.aa.com/content/travelInformation/baggage/carryOnAllowance.jhtml;jsessionid=5O4R3Z3FXS1AZEAJJNDU1DEQBFFS4VMD?anchorEvent=false

Thanks for the link Boyd,
I have a petrol PCCB 1N shoulder bag which I managed to get on a flight between UK and Korea and that's pretty bulky. It certainly seems to differ between airlines. I need the backpack as I find the shoulder bag pretty cumbersome for the mountains, I'm going to be using the PD170 in the Sierra Madre next spring. I think i'll do more research before I post a thread! Thanks for your help.
Patrick