Does anyone have experience with lowering the rear air suspension.

I have a 99 A6 Avant
Quattro with rear air suspension

I like to lower the car aprox 0.8inch (2cm)
At the front i can use normal lowering springs but at the rear i need to lower the air suspension.

So:
Does anyone have experience with the possiblities in lower the rear air suspension.
And can someone tell me or show (with pics) me how to procede.

All help will be welcome

 

its all to do with Citroen hydraulic suspension mate but I don't know where the height adjuster is on the Audi