Clip Confusion

I think I've said before I'm a pretty damn fine editor (if I do say so myself).

Problem is, how do I prove it? I've got my writing clips to speak for me, but what does one do to prove editing ability beyond the occasional copyediting and/or proofreading test?

Someone on one of my writers' groups suggested a Before and After style, showing an original piece and a version with my edits. Hmmm... Sounds good in theory, but, lets face it, most people who ~pay~ (that's important people... gotta buy mama a new red pen y'know) for freelance editing don't really want to advertise that they've done so--not dissimiliar to trying to prove you really do do ghostwriting in that regard.

So... How do you do it? So far I've been lucky, I've gotten one of my editorial clients who agree to let me show before and after versions of her piece, probably because it was just a press release, but, still, we all have to start somewhere.

If anyone out there in blogland has an idea for this, PLEASE let me know. I am ALL ears.