[neallewis]

The hudy setup book is very lacking in this area. the descriptons are either not applicable to the change you are making, or don't really relate to anything useful regarding lower roll centres and track width. it was written for 1/8th cars and i was left with more questions as it did not cover most of the settings on the xb4, or just a contradiction. Best to try them out for yourself in testing to get a feel for how they change the car. Nathan ralls setup is good for starters.
After my year with the xb4, i struggled to make the rear end grip on low traction, the car was always wanting to rotate. what i now know is to try a heavier rear diff oil and go stiffer on rear springs. These have more effect than the lower roll centres.
Also, xray put out an advisory to stop people using the innermost settings as they helped to break diff outdrives.