The name of the game for commercial aircraft is light structural weight so that more payload can be carried. Such helicopters with articulated heads are stress out for around 1.7 g's. Of course these aircraft don't do crank-and-bank stuff. As Gabor said, 4 G's is the normal minimum for a designed all-up weight. For peace of mind and yet not designed too heavy, I like designs that allow for 6 G stress and 4 G test load. A higher G load design also gives a higher fatigue life. Many FW high performance homebuilt aircraft are stressed to 10 G's, and higher.