How about an old school Brian Gottfried slice? This vid actually talks about "modern" vs "classic" slice bh but I start it at the (sort of) instruction part...
http://www.youtube.com/watch?v=0IKYI3CEOsk#t=03m15s
And don't ask why the narrator chose Roddick for modern example!
The clips in that slice bh vid originally come from this "sneak attack" video...
http://www.youtube.com/watch?v=xbEAS6pK0ms
-which come from here btw...
http://iws.punahou.edu/user/lcouillard/
When I start losing a bit of ooomph on my slice, it's usually cuz I start hitting it too far out in front, (get a bit eager) and get not so good weight transfer into the shot.
Amazing - can't find any isolated Edberg slice bh vids either!