How many can and do survive 16G seat loads.
Last summer I survived a crash where I was ejected through the windshield, having ripped out the 9G seat and seatbelt. That means my body was subjected to a minimum of 12G, though more likely 15G. That causes injuries, though is survivable. Through the evolution of the standards, seat and seatbelt strength requirements have been made more demanding - for the most part, going from less than 6G calculated, through 9G static load test to 18G dynamic load test. I have done STC approval projects on vintage aircraft for modernized passenger carrying (Grumman Goose was one), generally in such cases, more modern standards are applied to the STC approval. I have no specific knowledge of the Ju52, though I would think it might have had a seat refit done prior to re-entering passenger carrying service, and common practice would have that seat refit done to a stronger standard than original. That said, from the crash photos, it does not appear that seat strength would have been a factor in surviveabilty.