Those new corner screen pieces look to be a good investment for a tricky section to repair.
They are nice only a little tweaking and they fit great. The metal thickness between the two are about the same also. I cleaned up the firewall, threw some paint on it. Then I finished cleaning the pass side lower windshield corner, and checked how it fits. The pass side fits better then the driverside. Don't get me wrong, its not a bad fit there is just one spot weld that isn't touching form the old panel to the new. I think it due to but joint on the a-pillar.
The worst part was after I thought I had all the little pinholes in the firewall filled yesterday, I checked again today and sure enough there was more. I have to turn the lights off then I shine a flashlight from the backside and look on the front for light coming through.
Lastly I fixed the one rusty spot on my driver side front frame rail. Here is some picks of what is behind that little hole.
Lunch