At this point, it's not so much a "grille" as a "plug". It's also going to have an effect on the airflow around the truck (incresed wind resistance), thereby affecting your gas mileage. With it in the current form (as in the pic), you're now "pushing" the air with the entire front end of the truck. With a more open grille, some of that air gets through, doing the cooling thing with the radiator, etc.
Not only the engine cooling issue, but if your truck has A/C, it will have to work harder to do its job due to the restricted airflow over the condenser. Your truck has a manual trans, so the cooling of tranny fluid isn't an issue....but the overall underhood temp's gonna rise a bit.
If it were me, and I was dead-set on using DPaluminum for this, I'd lay out some rectangular holes say 1.5" x 3", and cut them out. Space them out....at least 1/2" apart....to retain the DP "look" (some of the raised ridges would still show in places).
Plus, the rectangular design of the holes would keep more in flow with the basic look of the front-end of your truck.
But....that's just my .02 on it.