Sorry I'm so late to respond. I'm not on the computer a whole lot lately
First off congratulations on your new Airstream. Geez, by now it's probably been well used (hopefully) and also hopefully this response is not too late to be of interest.
We tow the Coq frequently and have had no problems either way. We do make a point of hitting it early or late to avoid the heat of the day, and the traffic volume as well is down at those times. When we are in a hurry to get somewhere or the Coq and connector make sense that is the route we take.
The nice trip though, much more scenic and it is only 90 minutes more, is the old Hwy 1. No major hills, less traffic, slower paced, and beautiful scenery. When we've left enough time to take this route, which is the preferred route, this is the way we go.
We tow with vintage cars with my '57 being one of the newest and although we have upgraded them significantly they still don't have the same cooling systems as newer vehicles. We don't have problems but we travel at 90 K/Hr mostly.