My Superduty has rear window in 10x10 size, so only dogs can get through, but for me cooling on the road is main issue.
Often when we drive the camper is reaching 130-140F inside, so using it for lunch or bathroom stop gets pretty difficult.
When i set my truck AC to 72F and manually override fan to high, the camper gets comfortable with open passage.
That also saved one of our camping trips, when arriving at 124F campground - the generator died after 10 minutes of performance.
Running truck engine for AC for 5 hr let us sleep where nearest hotel was 100 miles away.