^^^ might i suggest something ? though i myself didnt do it cause my fender got fixed with the 0.5-0.65 inch underlay i used(was definitely much thicker than the one in the pic)...and i double layered it at the fenders.. byt maybe im satisfied cause my system is SQL and not SPL...sids is a monster 
but being the DIY'er that i am...for you sid...i will suggest this..as it aint permanent so worth a shot...
see this pic(its a city 2005)

so what u shud do is get a custom "brace" made from a woodworks guy... and put it between the fender and the "lohay ki patri" that is in front of it... and do it so that it is a SNUG FIT....use samad bond if u have to...and even self taping screws for the "patri" side...
this shud stop the rattling.. definitely...
enjoy !