Thank you, Rick3000!
A very detailed description!
I am not finsihed yet, but managed to get to firewall #2.
I wonder, where firewall #3 ends up inside?
Here are a few pics I took, showing the route, I am taking now (with the help of Rick3000 & 101 projects books: project 85).
The 1st photo...2 nice cable ducts (actually 3),
2nd photo...nice big rubber grommet,
3rd photo...hopefully easy accessible (from the cabin) firewall rubber grommet
