Hrm.. wouldn't it be more dangerous outside of the car? A good scrape through an n2o line with some spark from the SS line and it could be oops time that line stays pressurized all the time while you have the bottle open :\
Not to mention where are you going to mount it outside of the car? I didn't relocate the battery to the trunk.
I ended up going under the wiper cowl and through the rubber piece that is there to keep the leaks out. It run smooth to the left of the clutch pedal no where in the way and all the way down my drivers side under the door paneling up the right and in the trunk. It's invisible in the car and not existing to the outside elements and such.
Why would they rule you to have the n2o line outside of the car?