Was agreeing with everything that guy was saying up until the 'pay for my secret technique' bit. Granted what he was saying is mostly correct, however i'm always extremely wary of things like that. To sum up, he is correct in saying that most styles use the hips like a revolving door, which is simply nonsense for producing power. Our 'double hip' is easier explained by imagining a normal door, essentially only one hip is driving forward. It is called the double hip because we keep 1 hip in it's place, ie the door frame where it joins onto the wall and this is counted as the first hip, it's in place. The 'double' part of the hip s where the other drives forward without or with minimal movement of the other hip. I hope you can get what i'm trying to get across here, if you want, go to https://www.peterconsterdine.com and order the video/dvd, power strike. Peter consterdine is famous for being a really hard hitter and he does shukokai, he also is buddies with Russell Stutely who in my opinion is the main guy for waveforms, ie damn hard strikes. Hope you got something from that, any more questions on the 'double hip', i'll do my best to answer, i'm not great at it myself however.