Hey mezzy!
Try & make a few AA-guns, like an AK47 or AKSU47 (which is AK47SU in OFP, but its a wrong name).
As far as I know, all ya need is to put:
AirLock =1;
in the cfgWeapons part (or wuz it the cfgAmmo ?) ;D
That'll define the weapon as an aa-gun, if Im not all wrong. And yeah, the addon may derive from an armored bird - if "class helicopter" is the father, then try & add a few sub classes to the cpp, just to get it "down" to an unarmored helo, like the OH58 or alike.
just a suggestion m8