Sounds like you made better progress than I did. The problem is that this is one of those sounds that doesn't always appear to order, until the second the mechanic gets out and you drive off alone!
I drove mine for a good 20 miles this evening on the way home, just to find more situations that bring on the clonk. Still, the most prominent clonking comes in town at 20 mph and even less. In my car, you couldn't miss the sound from rear NS.