I added an additional terminal block behind the panel for grounding various items. It’s grounded locally through the jumper wire down to the 2″x2″ chassis member.
I had to remove the brake biasing knob to install the rivnut for the grounding wire.
While I had the knob out, I installed a couple of 8-32 rivnuts and used some of the torx-drive screws. I had previously used some sheet metal screws, but I’m trying to eliminate all of them.