I think there's an easy explanation for that Bill: AMD markings rise over the silicon surface. When positioning the block, at first the only direct contact surfaces are the high point of the leters, so whith little force the copper will deform. Only when the markings are engraved in the copper you get a full contact surface.
That suggest me that the ideal surface roughness of a WB to be used on an AMD cpu would match the roughness of the markings.
N8: It seems to me that you could be able to measure that roughness and tell us what sandpaper grit could be used to produce a matching surface?
