Voyager, if you are talking a stringer, you can rebore a new hole at an angle with a hole saw. When Grady builds the boats, they install all before deck is layed. I'm surprised so tight since they usually oversize as it always makes it easier. Why is your hose heavier?
I believe gas tank vent is 5/8 inch fuel line spec, what's yours?
Your aux tank is further back I expect, in any case don't loose the hose (old) as you route it, some get a PCV fitting and do a but joint and rivit/screw the hose so it so new to old continuous no surface transition.
Usually the fill lines are the pain due to diameter.