It doesn't make a lot of difference if you post here or in the Advanced board, a lot of people look at both. If you do ever want a thread moved, don't start a new one - just ask a mod to move it.
Regarding the question, you can't increase the armour without creating an addon. However, you can make it harder to kill. I would suggest adding an eventhandler "hit" to the chopper (and the crew) which started a script that does something like this
setdammage chopper1 ((getdammage chopper1) - 0.3)
If you're not familiar with eventhandlers have a hunt around the Ed Depot, there's some good stuff there.
Edit: I know you're frustrated but IMHO bumping your post after a mere two hours is inconsiderate to the other people who have questions on this board. If I'd noticed in time I wouldn't have answered your question now. Given the usual rate of posting on this board the minimum is about 24 hours.