You need to be a little careful re mesh size if considering installing a screen , sometimes you can get overheating at high speed due to change in airflow, had this happen on an earlier Jeep, it depends on the size of the bugs you are trying to keep out, do a little experimenting.
A piece of fly screen (the plastic stuff is much easier to work with than the aluminium stuff), a bunch of zip ties and a pair of scissors. Mine is behind the grill, but in front of the a/c condensor etc. A few strategic cuts and it will fit around everything back there, then zip tie it off all over the place. Mine is only attached at the top, so you can grab it and bunch it up level with the top of the grill if you are ever concerned about airflow / overheating and there aren't any bugs around, hence I leave it on permanently.