A few photos of the finished repair job. After trimming the corner I rebuilt with a knife and removing nubs sticking through the holes to the inside with a sharp putty knife, I used my little right-angle sander with a 25 grit disc to remove the excess and smooth things out.
The new plastic has a lower melting point than the original plastic, so during sanding it would melt slightly if I stayed in one place to long. So I’d work until it started getting tacky, then move to another area while that cooled and so on. Eventually I got it all shaped to my satisfaction. The screened over area still protruded a bit more than I liked – if I had it to do over again, I’d attach the screen to the inside and then fill the hole from the outside. A bit tricky to do it that way, but it would have turned out better.
I cleaned the area to be covered with heat barrier with Acetone and then cut out a section and covered it.
You can see it’s nice and flat except for one budge where the screen was applied. No biggie – it’ll be be hidden by the exhaust. I remounted the airbox once again to test the fit. So much nicer not to have all of those holes everywhere!
Now I can finally move on to the next item on the checklist…