I have found some data for the He111 here :
http://www.bredow-web.de/Sinsheim-Sp..._111_h-16.html
there one can read :
Safe load factor in recovering in relation to the aircraft center of gravity:
2,9 g at 11,6 tons
3,1 g at 11,0 tons
3,4 g at 10,0 tons
3,6 g at 9,5 tons
If thats the safe figures the damage should occur at much higher g-loads.