I would really recommend either Brian Kinwald's or Dan Griffin's latest set-ups posted on the set-up sheet page of the 2wdrc tech section:
http://www.2wdrc.com/tech/SetupSheets.htm
We've been doing a lot of work over here in the states to get the X - 6 squared hooked up on lower bit clay tracks, and made big strides in developing traction and stability. Try out either of those set-ups and I think you'll be very close.
What tires are used at the track?