Immediately straight up from the port, to reduce water ingestion.
then teed off on pilot side forward along longeron.
seems to be so much competing for the limited space in the 'tunnel', so mine is under the canopy rail forward to panel.
now, in hindsight, this area on occasion seems to be where I want to drill and bolt a fire extinguisher bracket etc....so it might have been safer halfway up the sidewall, shielded thru the baggage compartment, but then under the armrest and so forth.
On my 7A ( same fuselage as the 9), I ran mine down the left side and under the canopy rail. Drilled a hole in the bulkhead behind the seats. Totally invisible.
I ran mine beneath the baggage floor, then used a 90-degree push-on connector to run it up the center tunnel. Click on the photo, and you should be able to scroll back and forth through the album to see other shots.
+1 - Use a "y" connector at the top of the bulkhead for even length between sides, just in case it matters. Also, you can heat the tubing and make short radius bends (beverage can) for more tidy installation if you wish. I only learned that after the aft fuse work.