Mike
The second picture looks pretty straight forward, in fact it looks like you already removed one nut...I can not figure out the third picture...The only alternative I think is to drop down the coroplast enough to at least get an inspection mirror in so you can see the upper fasteners, then go from there...The coroplast is like a cardboard correct, not a fabric...???If the coroplast is like a cardboard you could also cut a piece of it to make an access hole and when your finished the repair just tape the cut piece back in place...