My experiences:
Trip A: Tri-X, Delta 400, Delta 100, Plus-X, FP-4
0. St. Louis to Atlanta--hand inspection, doesn't count.
1. Atlanta to Paris. Can't remember if hand inspected or X-rayed.
2. Paris (CDG) to Marseilles. X-rayed.
(We drove back to Paris--no X-rays.)
3. Paris to Helsinki. X-Rayed.
4. Helsinki to Paris. X-rayed.
5. Paris to Atlanta. X-rayed.
6. Atlanta to St. Louis. X-Rayed because we were in a rush.
So, 5 or 6 X-rays exposures, no visible damage.
Trip B:
St. Louis to Houston, forget to get hand inspection; one roll of Delta 3200 was in with the Tri-X. Houston to St. Louis, forgot again!
No visible Damage.
St. Louis to ?: Film in Domke X-ray bag triggered a hand inspection. Return trip: I had put the X-Ray bag packed against the bottom of the bag, where it fit best. It was against the frame and roller parts, and thus was presented edge-on to the X-ray. This did not trigger a hand inspection. The bag may have looked to the X-ray person like it was part of the bag frame or mechanism. Or else they saw what it was and were not concerned with it. No damage.
A museum of Judaism on the right bank in Paris wanted to X-ray my camera bag, a Domke F-5XB. Knowing I was going to exceed the five exposure limit, I asked for and got a hand inspection.
These are the experiences I remember.
The advice of the organization in the link that was provided, the i3??, to limit to five exposures, is consistent with information I found on a Kodak website. Looks like five is a good number to go by.