Rear Auxiliary Spring?

[syncrov69]

I like to have more info about the optionnal rear Auxiliary Spring. Is it a rare option? Is it possible to found easely a used kit? Can this option really improve the charging capacity? Do you have detailed picture of the plate with the rubber pad screwed on the rear axle/trailing arm? How much is logical to pay for a used kit(left-right)? Is it the option number G60? Thank's for all your answer and picture. Francois

P.S.:sorry for my bad english!