[sick472]

I've done a fair amount of welding up pin holes from inner rust and should say, first, that cutting out the immediate area and replacing with a patch is the best way to go...but, when welding up pin holes, the heat from the welding process will burn out any rusted thin metal and "show" you how extensive the rust damage is. You could find that you chase the holes out well past where they appear to be OR merely weld in the holes and be done.

I would consider welding the holes up first and if they burnout horribly proceed to cutting out and patching in. I say this because the roof is a complex curve and my sheet metal shaping abilities are novice at best. Also, my builds do not see day-in and day-out weather. So, the likelihood of the inner rust resurfacing is minimal.

On the flip side, by cutting a section out, you could do a more thorough inspection and see just how far the pitting extends past what is showing.