This is the method I have used for 44 years to adjust my mirrors. On my stock 2020 RAM 3500 towing mirrors, the large portion will not adjust out far enough in the down position. I also do not have to adjust any mirrors when towing any trailer.
Limit Blind Spots With Accurate Mirrors Settings - Driver Safety
All vehicles have blind spots or blind zones. Learn how to reduce them with these tips.
www.aarp.org