i've built 4 systems using the volcano7 w/out any shims. so as far as needing one goes,no. you do want to remove the pad on
the bottom,use a single edge razor blade to scrape it off.
artic silver is a great heat dissipator that you should definatly
consider using. when you remove that heatpad from the bottom of your hsf take a lint free rag ,some 90% rubbing alcohol,and
some acetone and clean the area where the pad was. do the same to the core of your cpu. next take a small amount of artic
silver(bb size) and spread it evenly over the area you just cleaned
don't use bare fingers, a pair of surgical cloves will keep body oils
from gettng into the pores of the metal base.remove any excess
artic silver w/the edge of a clean credit card or such,leaving a thin flim on the base. do the to your cpu, clean apply a small amount of
artic silver remove the excess. to much paste is as bad as to little!
doing the above keeps the temps on my xp 1800 @39c to 43c!
hope this helps you out!