Cut some shape into it like the original ones. Bent the cover piece over a solid bar with the nylon mallet.
Tacked in ready for welding. Now I had to clear the flange where the new section of floor joins to the donor floor. Rather than just cutting the flange away I thought I would press the clearance in.
With the longer piece taped underneath I placed another couple of pieces of scrap each side of it on top. Then taped them as well. Put it all in the vice and did it up nice and hard. Gave it a hit with a bolster until it left a mark in the tape right across showing I had the depth I needed.
Shows how I clear the metal now. Did the end bits as well to clear the flanges on the floor supports. The factory just cut it instead but thought might as well do it this way to get a better seal and stronger too.
Holding it up you can see how it clears both flanges now. I actually shorten the hump a bit before welding it in. Now for the other end. To terminate like stock it needs to go up inside the tunnel a bit. This reduces any stress rises. Just marked the flange where it last touched the floor and then cut to that point. Bent the flange around the corner.