Exactly. So if your going to just grind it home, and hope to remove the rusty shit, and not see the other side becasue of the inner supports, its like shooting in the dark. Without seeing the other side to see if its was effected, your better off cutting it out to A: see if your hypothisis was correct and the metal was rusted through to the other side or B replace it with 100% solid metal. From something rusted like that its guarenteed that it is rusted on the oposite side of that sheet metal. But since the inner support is far enough away from the outer skin, I doubt that the inner support channels got effected. cut out only the outer skin. spray with weld through primer. Weld in filler piece, done deal. fill prime shoot.
Yeah man I will do it up for you. How is the original paint? It will be fun matching that i bet. is the damage around a body line? if so we could spray up to that to hide the color differences if there was any.