You know, I probably should have used a 2D scanner instead of a photo.
Well, I think I've finally got a part that's close enough fit.
One surface that looked flat is actually sloped. My first cut had a same sized edge overhang all the way around, but the actual part varies continuously with a couple of notches.
All told I spent a good 5 hours and 3 prints. Would be nice if there were a good scanning service.