Fuel line through firewalls
Another two cents. I also have been flying more than 20 years and have a bipe with ten years flying on it with never a problem of a fuel line chaffing on the firewall hole. I certainly have no arguement with the several suggestions, but what I would add is to not forget to look out for where the chaffing DOES usually occur, and that's where it connects to the brass tubing if indeed you're using brass tubing. Be sure to not leave a sharp edge on it because it will cut the fuel line. Especially if the line angles away from the tubing sharply, as is often the case with a tank front close to the firewall. Happy flying!