It would seem after all these years if someone could be sued for operating a recreational/non-commercial vehicle over its GVWR, it would have been done by now. However, there has not ever been one case cited of where it occurred successfully. Like someone else said, you can be sued for picking your nose, that doesn't make it a successful court case. Gross Negligence is a high standard to prove.
I have read a lot of lawyers opinions about lots of things in my line of work. All reputable lawyer opinions come with citing of sections of law, case law, court decisions, etc. Any lawyer's opinion lacking such references is in my opinion, a waste of time reading.