I've never been too successful with polyphasic sleep, at least not the hardcore type (6x20m naps). That said, a lot of very successful people have adopted biphasic sleeping, taking a shorter core nap (4 to 6 hours) with a nap during the day. I think this is a better approach, especially if you're in a field where you use your brain a lot. Taking a 30m nap can do wonders after lunch.