I would just post the results of that panel. If the panel doesn't work as it's supposed to, and the manufacturer doesn't respond, then that is valuable information that people may want to know. No need to editorialize on those particular results. Just post them, and they will speak for themselves.

"Panel XYZ from manufacturer ABC, advertised MNO watts, measured TUV watts. Attempted to contact manufacturer about the apparent discrepancy and testing methods, but received no response."

Posting factual stuff like the above is fine. But editorializing by saying something like, "Manfuacturer ABC is a total *&%^! and I would never buy their piece of ^&*$ product!!!" might get you into trouble.