Here is a paper by Pierre Lurne, the designer of the turntable that discusses his bearing. I think that you have to get the right taper on the point of the shaft or it will be able to move on the seat. How high off the plinth does the platter run?
http://www.enjoythemusic.com/magazine/manufacture/0208/index.html
http://www.enjoythemusic.com/magazine/manufacture/0208/index.html