The slip joint is double wall and the primary slides between the 2. I had a slip joint on a 6 into 2 (yep, inline 6 with headers) that wasn't double wall and it never leaked so I'm not concerned. My guess is it was the only way to get them up to the engine from below. Having been under the car recently investigating and deciding if I wanted to do it myself, I don't want to do it myself. It looks impossible. But, not my problem. I have a fixed quote no matter how long it takes.

Les