Do like I did and put some ribs back in the new patch. REAL easy. Stick the metal up on the vise, open the vise about as wide as you need the rib to be and take a deep socket just a little smaller and stick it on the metal right above the open vise jaws. Take your hammer and start gently pounding the socket and metal down into the open vise jaws. Just keep doing that until you have your rib as long and deep as you need it. If you look back at my thread, you can see where I did that on each side in the extra filler panels I had to make because the rust went further than the panel. It's real easy to do. That way, you won't lose any strength in the floor.