I got caught up in the fad and tried hard at polyphasic/uberman in 2005, for like six months. It would almost work, but I didn’t feel good, and once in a while instead of waking up after 20mins it would be more like 12 hours and I’d feel even worse. I read somewhere that schedules like that were developed to temporarily get people through life-and-death situations where a long sleep just isn’t possible, and was never meant to be a lifestyle, and I never tried it again.