Ah, I see what you were getting at now euroherbal, but I just think this doesn't work out either. I don't believe the set wall gives any indication that the floor is actually on an incline when Vader initially steps down towards the smaller, circular prop. It's just the shot panning down that may give that impression. On top of this, I don't remember any of the other shots of Vader's 'chamber' supporting this notion either, whenever we see the set...

I'm not sure about your actual '8' shape either at the end of the day, but I've noticed something else to think about now...

You'll notice in adywan's behind-the-scenes shot that the 'light grey' circle on the floor is cirling behind Vader on the platform...but in the bottom shot on my previous post...the 'light grey' circle is circling in front of him. Things have been moved around compared to how the behind-the-scenes shot is layed out...