So I got to thinking.....
The case ground of the converter is there in case internal wiring of the converter breaks and shorts to the case.
If grounded to the chassis, isn't the chassis grounded to the negative terminal of the battery?
Not sure what would happen to the battery if it were to try and ground 120VAC.
It isn't like it would go to an earth ground, the trailer is on rubber wheels and I doubt the jacks would be a sufficient grounding source.
Also, if the DC side of the circuit fails, and I ground it to the AC side, well I am sure fireworks would ensue.
So in conclusion, gonna forgo the case ground.