TR-6 pinion seal leak

["Vito Pacione" <classic@m2.interserv.com>]

Does anyone have a preference for the rubber polypropelyne seals over 
the leather pinion seals. Does the rubber create more wear on the 
shaft?
I am also concerned about the leather seal leaking when the car is 
not driven much and it dries out.
Also, is ther any trick to installing one so as to lessen the chances 
of a leak?