I used the seat base bolt, with the paint ground off.
Or you can drill and nut and bolt to the seat base.
Or you can drill and rivnut to the B pillar.
Or you can drop through the floor grommet and drill and bolt into the lower chassis rail.
Or you can go a bit further back and drill and bolt, in the framework behind the first panel in the back just behind the d pillar at a low level.
Or you could just drill the floor and nut and bolt there, but that will mean getting up under all the trim panels off your tank or exhaust etc etc so that's a pain.
...
Because my new inverter cables are so fat and beefy...
I think I will be drilling and nut & bolt (with serrated washers) to the closest inner piece of chassis framework I can so that will most likely be behind the panel, that is behind the B pillar so basically right next to the inverter. Assuming I do place it there.
My main battery Meg chassis connection will be the seatbase bolts.... Again sand it down and make clean for a good connection..... Or I will take the feed to the base of the B pillar and drill and nut and bolt and no connection onto fresh body work.