No not all in your head, I use the 7.5x55 Lee Collet Die for the same purpose.  I can size the neck just enough to get the neck tension I want.  I have to use a washer between shellholder and collet when doing 30-40.  Parashooter's idea is a good one too.  There's no drag on the mandrel of the collet die unless you've put enough pressure on the collet to leave marks on the neck, which of course is overusing it.  The 7.5x55 die only sizes about 2/3 of the neck, leaving the expanded rear of the neck the same size it was when it came out of the chamber.  Maybe that helps with bullet alignment, maybe not.