Help W/ sheet metal

I still have this task to accomplish as well. I keep starting on it and then giving up and I've been a fabricator for 15yrs. Kind of a pain in the a$#..... I was thinking the other day I'm going to try and do it in pieces and weld them to the factory "v" brace. It's hard trying to make one large template all at once. I don't think it needs to be all one piece, it just needs to be sealed off.