And, BTW, no one really gives a tinker's dam what tartan you wear. As the Duke of Kirkaldy pointed out, many military tartans were not exclusively military, and none are propriatary.
As a Marine, I'd be just as happy to see you in Leatherneck Tartan (the proper name for it, designed by my fellow Marine, Bob Hall) as I would to see you wear a tee shirt. It's a great tartan.