Some people may disagree with me on this, but I think you will do better on the straights to stay where you're expected, and not move right, then have to move back left into other traffic trying to set up for the end of the straight in the same space you are.
I would ride 4' from the left side of the track, leaving a little room for people to come around you on your left, and a LOT of room for them to pass you on the right. (which would be the courteous move, on their part)
The worst-case scenario for you is two riders coming up on you, riding nose-to-tail. The front rider sees you, but the guy on his ass doesn't. If the front rider waits until the last second to go around you, the guy on his ass may not react quickly enough to avoid you. I lifted the rear wheel on my F3 when I was the guy on the other rider's ass. Lesson learned. Almost the hard way.
But having a slower bike move across the track to set up for a turn is more dangerous, IMHO. Just leave room to be passed on either side. I would honestly be looking behind me if I were on a bike with a 100 mph top speed. I wouldn't advise you to do so, but I would...