KMP sells bomb releases with a scale bomb, and there are bomb releases at my LHS, so I'll use one of those.

As for the pivot arm, I know it reeled back up in the full scale one, or it would have caused drag and banged the deck on landing. I'm not sure how it reeled up though, I'm guessing hydraulics. I'm going to use a basic stamp and a servo connected to a winch on mine. A spring would work better, one designed to drop under the bombs weight and stay when not, but the bomb would have to be heavy for that, and a heavy bomb can do serious damage if it hits somebody.