I welded the stiffener into the right rocker tonight. I punched holes into the top flange with my pneumatic punch/flange tool and plug welded the top. The bottom flange was just edge welded. I figured I would weld this up off the car since I already had the experience of the driver's side, so I knew the measurements and how it was supposed to fit together.
I used the stiffener I had fabbed up at a local shop, and I'll have to say it fit better than the one I bought from KGPR. I paid $30 for the locally fabbed one. Now that I have all the measurements, I'll have them fabbed if I ever do another rocker job on a vert.
I found out the paint problem occurs because the paint has been on the shelf too long. Good thing is, they have a reducer, DTV, that will thin the DP90 a bit. I think you can see some of the spattered texture in the pics.
Stiffener welded in