I've found the TSA in the US very helpful. I take a very "English" approach by apologizing for causing them trouble and asking them if they wouldn't mind helping me out and hand inspecting the film for me. I'll often add that my client is a pain in the .... and every time they've been happy to oblige. In most instances, when I thank them they tell me that that' their job. The last time I left Heathrow however hand inspection was refused because the film wasn't ISO 1600! The security l"lady" did not want to hear about degraded shadow densities and her reaction to my mild protestations suggested that I was headed for the medical attention that Jason warned of!