Braded steel line yep, you can get away with that length inside the frame may last you 20-25 years or more. I was thinking steel hard line, and brake hard line. Also the ability to have it where it can readily be seen to inspect it when under the car. Cant do that if its hidden inside the frame. Getting nice tubing insulation where the outside is covered in a high heat compound.slide it over the lines, attach inboard of the subframe connectors. Only spots you need to really concern yourself with on the insulation is where the mufflers sit. As long as you have 8" to a foot of clearance between hot exhaust and your lines the heat from the pipes shouldent affect it. Even short runs in an aircraft are secured every 1.5 - 2 feet.
