Unless you have the original 3 piece rocker parts, it is very hard to replicate
that setup. Ours is a 2 part deal, where the middle and outer are combined. So the 2 pieces meet with a flat flange at the top ans bottom of the inner rocker. You can add drain holes or slots if you like. Made of much thicker material (.059") than the original (.040"), you get strength and better resistance to rust-through. The original outer skin is a very thin piece, whose main function is to create the body contour. That gentle curve is formed by bending the outer piece into place and holding it with the spot welds. If you section it and break the spot welds on one edge, it will spring out. Our fabricator replicates that curve in our outer rocker. It is 32" long. More than enough to accommodate the straight section between the fender and quarter panel seams.