Just to check back in here...I flew from Richmond, VA to Huntington Beach, California this week. I was actually able to put a nice jacket, pair of pants, 3 undershirts, socks and some toiletries in my GPC back over my P2. I then carried another backpack for laptop and remaining items. Carried on both items and the GPC fit in the overhead on both connections (737 and MD-83). I had a battery in my P2 and 3 other batteries lined up in the case. Not a single word was ever mentioned nor did the conveyor even slow down through security. I'll definitely be taking my P2 wherever I travel to this year (Have Puerto Rico, London, Toronto, NY, Boston and Chicago coming up).