http://www.overclockers.com/articles608/
the ENTIRE issue of mounting variability revolves around 2 aspects:
applied grease thickness, and
clamping force (and uniformity)
I do not run at 90% of the (old 24lbf) AMD max by accident,
and I would add that I know of no
data based on the 100lbf limit for P4s and the Hammers
(Ben, did you read that book ? - do so, you WILL like it)