The problem is getting past the rust. The inner fender lip is one of the more rust prone areas, and the patch doesn't include the inner fender lip. The fender lip--the part the patch doesn't include--is the difficult part to repair. I have seen pictures of patches where the inner fender lip was salvaged, and I question the integrity of the salvaged metal. (If you're not going to remove all the rusted metal, you're wasting your time and money, so you might as well use rust treatment, then fill the rust hole with bondo.)

The extractors on the 9 pose problems too. Considering that you have fabricate the patch into the area, the repair work is fiting the patch in the area. If you aren't replacing the common rust area of the inner lip, a hand fabricated patch will automatically follow the contour of the fender as you work the patch in, meaning that the patch panels are a waste of time and money. And lots of people, like myself, who have ordered the patch panels and sent them back share the same feelings.

Before you buy a patch, start cutting out some of the metal and see how extensive the rust is. As a rule of thumb, a pinhole represents extensive rust at least 6" past the rusted area.