Took me a while to find the main left-right bundle route so will put these here for future reference.
To add wires and a cable to the main left-right route I had to add an access at the place shown in the first photo. Be careful NOT to go past the bottom of the structural floor due to risk of cutting into wires and water hoses. The new wires had to run from right to left due to interference points.
Following is from Owners Manual for orientation:
Good idea to leave heavy string in the raceways to facilitate any future wiring additions.
To add wires and a cable to the main left-right route I had to add an access at the place shown in the first photo. Be careful NOT to go past the bottom of the structural floor due to risk of cutting into wires and water hoses. The new wires had to run from right to left due to interference points.


Following is from Owners Manual for orientation:

Good idea to leave heavy string in the raceways to facilitate any future wiring additions.