The VP-X manual says I will need a grounding bus maybe even two. Doesn't seem like I'll need two so installed just one for now and will do another when needed.
Bought this from Aircraftspruce because is mounts securely to the firewall and has a bolt to fasten a cable to the battery grounding point.
I decided the position needed to be somewhat close to where the wires are coming into the electrical bay and near the VP-X but also totally available to me after the top of the fuselage is sealed up. So I did NOT put it above the horizontal bar at the top of the firewall. I put it below. I can see it and access it from underneath. You can see it above the pedals on the firewall.