The axle position is determined by the through bolt and the upper and lower U bolt brackets so is set. It can be altered with a spacer plate, and Mulfab do one for the pre 06 cars where the axle was forward compared to the wing curve, but the spacer plate lowers the rear by a few mm. I did buy this kit for the Roadster, but haven't fitted it as I'm not keen on lowering it, even by a few mm. I might test it out if I replace the leaf springs in the future.
We had a 40 mile run out today, and the rear is better damped than with the originals, but still crashes occasionally - we have bad roads in South Yorkshire. It was a good shakedown for all my recent mods, and everything worked as it should, no knocks from the tool tray which is good!