http://mittlerbros.com/rear-end-narrowing.php This is the housing fixture that I use now. I used a borrowed one that was made by a tool and die maker for years and then decided to buy my own. I use it to check the housing, but when welding the tubes to the center casting you don't get much movement in the tubes. I weld about 1 1/2 inch on one side and rotate it to the other side until I get all the way around. I was a DOD aircraft certified welder for about 10 years, so I got pretty good at welding.