Here is more specific information on the battery issue from our DOT.
Safe Travel
For Lithium batteries like the 123 used in our flashlights, the Lithium content is 0.55 grams. This is from the Energizer web site:
http://data.energizer.com/PDFs/transportlithium.pdf
These are well below the 2 grams per battery limit for carry-on provide measures are taken to prevent short circuits.
I think the Surefire SC# is the best way to go. You not only have a place for the spare batteries, you have space for the spare lamp assembly too.