One factor not mentioned in this thread is engine size. A larger engine puts off more heat than a smaller engine and MAY cause some recommendations to be classified as requirements. For example, a year ago due to my extraordinary engine building prowess, I left a couple of paper towels in the engine compartment that found their way into the center of the cooling fan with predictable results. I did a lot of data tracking before I dropped the engine again and found the culprits cozied up inside the fan. I removed the paper towels and reinstalled the engine and saw normal conditions return. While I was testing, I did not replace the perimeter tin.
Those normal conditions are 180F oil temperatures under all conditions when the engine is warm. It doesn't matter if the engine tin surrounding the outside perimeter is installed or not, 180F. Remove the doghouse internal oil cooler and only use the external oil cooler and fan (replacing the doghouse tin with the older tin) and you still get 180F. Intake air temperatures are similarly stable running 140F-150F regardless.
I didn't put a hole in the firewall because I placed a big air conditioning heat exchanger there (another reason I dumped the internal oil cooler since it heats up that area). I don't have a rain shield under the grill, I did put a cutout behind the license plate, and there's a rectangular cutout on either side next to the plugs that I've never attempted to seal. Net result is that there are holes nearly everywhere.
However, my mildly massaged 1776 runs at normal temps all of the time. Granted, a hot day where I live is 92F. But, I do drive up mountains and get caught in slow traffic at times with no temperature creep. I'm thinking that my engine is small enough that it is more forgiving with regards to airflow. It certainly isn't my extraordinary design skills.