R6 rear shock on the FZS600

[kebab19]

Yay, the mod lives on 
The filing mentioned above is only for the 2006-07 R6 2c0 shock: if you have one of the 13s (2008 onwards) shocks as per picture then no filing is needed.
Spacer can go on either the top or bottom, most people prefer it on top of the spring.
Thickness - well, the Faulkner springs are 152.5 mm long whereas the original R6 spring is about 165mm long. So the extra spacer is to take up the missing spring length.  It can therefore be between 10mm - 15mm thick, depending on how much preload you want on the replacement spring.