Worked on the frame over the weekend - to install 'C Notches' for rear suspension clearance. My frame rails didn't have notches from ASC - and I've been planning to add them all along. 1) Notch Material - Go With 1/4" : I was going to bend up a piece of 10-gauge material (same thickness as the frame rails, but decided to use two 1/4" C-Notches that I purchased from the 'Welder Series' guys. After thinking about it, I think the thicker material is a good thing - makes the notch area stronger . . . as you're taking a pretty good 'bite' out of the frame. Also, having the 1/4" thick notches gave me enough material to radius the ends and edges nicely - the end result really looks formed, not fabbed. 2) 1/2" Plate Stiffener - Welded Inside the Frame Rail: When I originally started the frame - before I put the boxing plates in, I bent a piece of 1/2" thick material to weld into the outside frame rail - right above the C-Notch area. I welded it in the the frame and also had 4 rosette welds on the outside. This is important - it really strengthens the C-Notch area . . . I'd highly recommend something similar in any notched frame. 3) Measure Once Again - Using the Spring Hanger Bracket: I grabbed one of my 1/2" spring hanger brackets and sort of mocked things up - just to make sure the notch was in the correct location. I'd originally marked the boxing plates with the location - wanted to double check. 4) Cutout the Notches: I marked the rails with a black felt pen and used a plasma cutter to do the initial cut out. Then I used a carbide rotary file in my air grinder to finish the cutout, get the radius exactly right and the fitment the way I wanted it. Notice the 1/2" stiffener on the outside of the frame rail. The 1/4" notch plate butts up against the stiffener - keeps things as strong as possible. 5) Tig Welded in Place - Used 160 Amps: Wanted to make sure I had a lot of heat to ensure a good penetration of the weld into the 1/4" notch plate. I beveled the C-Notch edges so there was plenty of gap for the weld to fill - as I would finish grind the outside of the rails. Will post up above - the finished results . . .