let me clear up, in case there was confusion, the clamp the pieces/cut both sides method is only to get the new piece to line up exactly with the old piece. you dont leave any of the old metal behind the new metal. I think I left a picture out of my previous post.
clamp and cut
remove old piece
weld in new
clamping it and cutting it saves a lot of hours fitting the patch, it already fits because you cut out the old metal and cut the patch at the same time.