Mike, If I were you, I'd remove that narrow piece between the 2 areas you already have cut out. There is a brace under that area, and you should be able to grind through the spot welds pretty easily to get the floor off and keep the brace. If you can weld in 1 large piece instead of 2 small ones, you will save yourself about 3 or 4 feet of welded seams...

Rich