hoping you can let me know how bad you think this could be....

Here is another shot

I am hoping that I can grind it back, treat it with Por 15 and then fill, prime and paint.
My concern is that it will have spread to the inner sills. Any thoughts?
I also have some rust on the bottom of the offside front wing near the sill. Here it is

Is this going to be worse from the inside?
Any help or advice would be most appreciated.
Thanks






