Rear spring setup

[suggy007]

After watching this video
http://www.youtube.com/watch?v=u81xTfg5ZCA
he says have a 1mm to 2mm gap from the rear pod to the chassis
but underneath the rear pod were u build the rear springs posts there is a nut which is about 2mm thick
just wondering how people set up the rear springs and how do u gauge it cheers