I was disappointed with the paint, it came out much more glossy than I had hoped. But you can't really even see it behind the grill, so it's not too big of a deal. I ended up attaching it by using long drywall screws through the plastic tabs, parallel to the coroplast. This locks the coroplast in, and holds it pretty well. I had to use some zip ties to secure the edges, otherwise wind would flex it too much. Then I used some electrical tape to seal off any gaps. Not sure how the tape will hold up, but it doesn't really support or hold anything in place so it's not critical.
I've started to work on a lower grill block as well, using the leftovers from the sign. I have just enough to cover the lower grill if I leave some open for the radiator. Not sure how I am going to approach this one yet. I need to take off the bumper to see if it can easily be installed behind the grill.
