By loking at your work I beleive you are capable of adding metal to you visor to get it to lay straight across rather than have a bow to it. It would take some work but you could draw a level line for the visor add metal to the front or back of the visor to get it to be straight in the front. I am not real good at explaining things but will try to post a picture for what I am trying to say.
Edit by the dumb one: Hope this explains what I am saying it would take a little work but can be done, if you want to keep the front edge just would have to angle cut and fill in the pieces , go slow when welding . just an idea on my part good luck