The bottom piece is all you end up using for this repair. It is a little more difficult to do the finish grinding with this set up, but you don't mess with the integrity of the original machining. The line is rough cut with a cut off wheel in this pic. I sanded it to fit in place before I welded it onto the frame.
You can see the fixture that I use for locating the repair piece in this pic. It has six mounting points, so I know that the center stand holes are in the exact spot that they are supposed to be in.
Here you can see the piece welded onto the frame.
Here is the backside with the fixture removed.
Here it is all welded up. I am very satisfied with how these repair pieces worked out. It is a lot less work than making the missing pieces from scratch.