I went to the local hardware store to pick up a few items for the house and came across a "Make your own" Coroplast Sign kit for $3.83 (like this
I cut it into two pieces in order to fit in the lower grill area, utilizing the metal post as a divider, reinforcement to the outer edges, and allowed me an easy means of secure attachment (zip ties) to the inner grill.
I have a 200mi mixed city/hwy trip that I will be making tomorrow, where I will be monitoring the engine temps, and provided that it stays within reason, I will finish it off with 100mph tape around the edges to fill in the slight gaps and make the outer edges more securely fastened.