I don't know what the answer is.  My TT 46 pro is slick as a whistle, the wind will move the prop around.  But there is still a pinch fit at the top.  And it runs great.  I have had a set of bearings for it but no need to change them yet.  I do use blended fuel and always make sure there is
Castor in the mix.

Cheers,

Chip