Firstly, the guys at Stevenage may well have been "lunatics", by the same token they were not fools. The rollers in taper bearings are larger in diameter than the cup+cones of the originals. This means that the movement of the tapers is less than the balls, consequently the wear pattern will be over a smaller area. When your "new fangled" bearings have done the same ammount of work as the originals(if you ever cover the same mileage!) They will not respond to a small adjustment as the tracks will be indented. Your steering will feel life a threepeny-bit(if you remember such things). Not all "improvements" are for the better. Be forewarned. Roy.
Whats the point in taper rollers in the swing arm then?
The movement in the swing arm(sorry, RFM) is much less than the head bearings, or have i missed something here?
Probably something to do with surface area? (every bike after 1975 i know uses taper rollers for steering)
Ref improvements: hammer the standard bearings (accident or big pot hole), you´ve more than likely got micro dents in the race!!!. With rollers, you´ll bend the forks firstt