Chofetzchaim: i read the article you pointed to and immediately felt like i was reading something straight out of my spam folder. Indeed, that is not far from the truth.
Because you said tzorech iyyun, i did the requisite due diligence and felt there is good reason to discredit the advice of “Doug Copp”. A simple search will reveal the American Red Cross response to his method, as well as a snopes article attacking the man#s credibility and character. Suffice it to say that it would be far better to follow the advice of accredited safety organizations over that of a self proclaimed expert.
Bottom line is the best advice is to crawl under something that will protect your head from falling objects, and hold on to it. Lying down in open space seems not.to be a good idea.