Regarding the scrub radius,I assume this can be altered by wheel offset etc?
Yes, within reason. Sometimes scrub radius has to be somewhat of a compromise due to tread width, etc. and the tendency of the tire to contact the inner fenders, wheel to steering arm interference, and such. The further apart the intersection points are at the road surface, the more the tendency will be for the tires to follow ruts in the road and other pavement irregularities. A few years back the fad was to install very small-diameter wheels with wide tires on some of the riceburners, with the tires stuck out beyond the fenders a few inches. Those things were impossible to align, and they were terribly unstable.
Jerry