Triggers do not work too well, as your trigger bounding box is much larger than the collisions box. Look in the mission editor at yourself, another player or a bot.
You could try using the packaging you suggested as well as Armor::OnImpact, like this:
package ImpactChecker
{
function Armor::onImpact(%this, %obj, %collidedObject, %vec, %vecLen)
{
if(%collidedObject.sillyvariable)
{
//Execute whatever code you want.
}
Parent::OnImpact(%this, %obj, %collidedObject, %vec, %vecLen);
}
}
ActivatePackage("ImpactChecker");