My experience with the Custom 8 as opposed to the regular Custom was a bit of a softening of the highs and a bit more push in the mids. About the same output, but definitely less bite.
I like "Custom" family. I had owned some CCs and C5s and i still keep this C5 on the bridge of my white RG. My aim was to achieve more of a images and words era petrucci tone but in a Duncan-kindo way.