Like Tigerstyle mentioned, I usually turn the head. I also use the no look version, which we started calling the “point blank 360” (even though it’s only a 180 ;)), which is the spinning back kick that I use from inside punching range, but only if I can get the necessary sidestep to make them follow in a tight circle.
For all spinning back fists, I always turn my head. Like JWT mentioned, the head is where I start my rotation. If it doesn’t lead, my backfist is just a snappy one with no real need to spin. When I turn my head for the kicks, my shoulders and torso feed the momentum to my hips, which is where I need the power to be, and by that time, I’m already looking at my target. Also, my hero Kazushi Sakuraba used it very effectively (he turned his head first as well) against Vitor Belfort, in fact the first one he landed, Vitor had to quickly shuffle away, then he dropped to the mat and started butt scooting. I was in shock, I thought Vitor had the better stand up skills, but I guess he felt differently after eating that kick.
I get my head around first. 1) It keeps my spin tighter which also helps my balance. 2) There is less time spent in the risky position of not looking at your opponent. You know the one where they jeet tek your kicking leg and then eat you up because you can’t even see them. 3) Visualizing is great if reality continues to reflect the visualization but even if he/she doesn’t blitz you, he/she may move enough that the targeting has changed substantially. 4) I like having torque in my body when I kick. The head leading will cause your body to twist as you pointed out. This means your hips will have some torque in them when you deliver the kick. And in my experience this makes the kick stronger.
-myosimka
I totally agree with every point here. We’ve got the same kicking theory…this is creepy, but I guess it’s just like why my bro and I have so much in common with Ap Oweyn. It’s because of all the crappy martial arts flicks that we watch!
Gary Daniels for life!! (or president, which ever would help the world more). I don’t feel that the “no look, visualizing” version is wrong, and from what I’ve seen, there are plenty of people that get more power out of it, but from my experience, it’s easier to jam, if they don’t set it up properly. Even if they don’t set the head turning version up properly, they still seem to be able to bail out when they see me chambering the jam. It really sucks to be jammed out of a spinning back kick, but if you’re not looking at your target, that’s like wearing a big bow on your head, cause it’s Christmas for me 
On a side note, though. I don’t try to jam unless the opportunity arises, I usually get out of the way. Mostly a quick back shuffle, but on the rare occasion that I have enough composure to off angle, I can end up right behind the guy.
Here’s my question now…How many of you have landed a spinning hook kick in sparring? It’s a much harder kick to land, huh?
Your head better be around when you attempt that one, unless you plan on just flying all the way around with full momentum, and hope something is still in the path.