There is a trophy Huey a few km from my house. You can touch it and it always shocks my how thin the skin is. Logical but I'm sure I could push the blade of my Swiss army knife right through it.
There are probably a number US Helicopters as "Trophies" in Vietnam. We lost over 3000.
And yes, field dressing were both white or OD. And sometimes they were "improvised" as jammy said …
Had many flights in UH-1s when I first went on active duty in '79. Especially with the 101, in '80. And even a few as a cadet, in '78.
Didn't think the skin was that thin ? And I think the rotors are more durable than that? But I never tried or wouldn't do anything to damage "my/our ride" …
Of course like almost all aircraft design keeping the airframe as light a possible is always a consideration. I've heard B-29 crews were surprised how thin it's skin was.
An interesting anecdote about the Huey and weight. When my Bn in the 101 deployed to Panama, the CZ. By about 11:00 hrs, the air was so thin in that tropical heat. A fully loaded Huey, heavy with troops & equipment would literally would have to get a running start to get airborne. To get enough lift under those rotors.
We'd sometimes have to reduce the ACL[Allowable Cargo Load] as the heat of the day went on. You could squeeze in about 7-9 fully loaded Grunts in a Huey. But at times IIRC we'd have to reduce that to 6-7 … IIRC … 
Of course many times we'd start ops in the middle of the night/"0 Dark 30"… 
says he's pretty happy with these babes...
