Not that I have most of the electronics in place (at least temporarily) at the instrument panel, I noted that most of the ground wires I created were far too long. It's good to have slack, but this was a LOT. So I cut back the wires, relabeled them, and put on new Faston tabs.
Then I routed the wires forward to the common ground block and secured them (photo).
Ground block at the upper firewall, inside the cockpit.