at DC too. I got my portraits 3 times from Wal-mart before I passed the requirement. Good thing is Wat-mart only charges me once. But that was still inconvenient.
I used to take portraits at my home. I used Photoshop to size it. I never had an issue. If you have a PS, you can make 6 portraits into one 4x6 or 5x7 and have it printed. It seems the ambassor pays more attention to size and shallows from my experience.
Good luck!
Alex