the parcel shelf has holes already cut out for speakers....the holes have a diameter of 13cm, but then if you include the mounting holes into the diameter, it comes to 6"
ive drawn a basic diagram to show what it is like...theres the hole 13cm, then the mounting holes ring (grey) at 6" then the outer ring could be the cover over the top?

diagram if img doesnt work
cheers for any help.