I would e-mail them both and tell them that you are going to neg them unless they make good and then follow through with it. We'll see how bad they want to keep their 100% ratings.

You will probably receive neg feedback in the process but it will be obvious that it is retalitory. A neg is going to hurt these two sellers worse than it will hurt you and 6 months from now it won't even be a blip on the radar screen.

Cheers!
Bill