Being a level 6 Commander Center I have not won a single defense against a pure chopper army, I never come close. AA guns don't do anything because they focus on hinds while the thunderbolts blow them up. If you have too many AA guns then you open yourself up to S-13/Buggy spam. Is there anyone else that has defended against this? My new layout did some damage but even with 12 friendly choppers they went though my base no problem.