I have been traveling with a Filmguard bag. Sometimes they take it out and ask for a hand inspection, sometimes they don't they rarely insist on scanning the films themselves outside the bag.
Regardless never check-in your films. Nothing can protect them from the powerful scan for check-in luggages.
When a TSA x-ray operator sees an opaque bag on the screen, he/she just turns up the exposure until the contents are visible. Not much help there for your film.
Turning up the exposure on the screen does not do what you think it does.
With a line-scan X-ray, the bag is well out of the beam path by the time the operator sees the image. But it's probably coming in through a 12 or 16-bit ADC, so there's a lot more range than can be effectively displayed on screen (at least with a simple linear+gamma mapping). It's a matter of adjusting the display mapping to see inside denser objects.
The X-ray source power needs to be high enough to deal with the worst case scenario of large/dense luggage. If you can give your film a 10x lower dose while still allowing enough X-rays through that the operator can clear it, that sounds like a good idea.
It just has to be traded off against the fact that deliberate shielding is likely to be frowned upon, and they may take the film out and run it through "naked" anyway. Seems worth a try, but I'd definitely use a commercial product marked for the purpose and resist the temptation to DIY it.
