My opinion here is worth less than 2-bits, but here it is:

I spent most of my 8 years in the US Navy in combined units with Marines, most of it in Central and South America with a few side trips to sandy places. I have a true respect for any and all Marines. I haven't chosen to wear the leatherneck tartan, mostly because I'm proud of my Naval service, the history of the US Navy and wear the Edzell tartan.

But...

The one and only reason I would even consider wearing a leatherneck tartan, would be to honor the men who I served with: A Gunny who truely taught me the meaning of leadership and sacrifice for the good of the men and a Lance Corporal who taught me that devotion to duty was an honor and reward in itself.

That being said, I would do exactly the same as Col. Mac here, and ask the Marines who would have some insight. Its not being a poser if you honor, in my opinion. Funny thing, never minded having to wear their BDU's, but a leatherneck tartan (official or not) I'd still talk to the Marines.

Good on you Col. Mac.