I am contemplating purchasing an automatic gear hub, namely the SRAM Automatix. One of the criticisms leveled at this hub is that it shifts up too soon. The default settings can however be adjusted if know what you are doing, as this article explains:
http://mccraw.co.uk/sram-automatix-review/
Would using a smaller chairing on the crank-set have the same effect???
(I would rather do this than mess with the delicate innards of the hub axle).