G'day Ned,

Well as you can see from my set up the Aux Fuel Tank prevents running the piping down the inside.
But as you can see I got a pretty good gentle run from the OEM flange out under the rail and into the box with my Flex Pipe mod. It sits up clear of the other dangling OEM bits, so is not an issue in that respect.
I've been thinkin' a bit more about it and will wait until I get back and take the truck down to an exhaust mob in Adelaide and see if they can mandral shape me a nice 4" piece to replace the Fexi tube. And go from there as I'd like to still replace the squashed OEM Down pipe with a mandral bent 3.5" and step it up to 4" the rest of the way.
Bumped into a joker in McLaren Vale when home last as I hear a Powerstroke cruze in and park.
Me and the missus had to go over and introduce ourselves and get a look at his truck. Turns out he only lives not far from me.
It was a brand spankin' F350 4x4 Lariat 6.7Ltr Powerstroke CC. Boy did that thing look and sound smart. He was a good bloke and let us jump in and have a good look. As soon as he got it through the DOT rego he got it Chipped and got the EGR, CAT and OEM box all cut out and ditched for a straight pipe and the pipes leading out the back same as your with 2 x 5" tips.
He's had 2 x 7.3l before this one. He told me the mob he got the exhaust done with so I'll go down and see them when I get home again.

Cheers,
Reg