I have the same problem with my 2019 f150 Lariat but the 5.5 box. I currently have dealership looking into it with their engineers. I know my trailer hitch is adjustable and can counter the downward angle but I’m still worried about the receiver assembly not being able to accomodate the tongue weight at that angle. I’m no engineer but in my mind it could be a legit problem and I have my family in the truck 80% of the time I’m towing. I’m curious if you have gotten any further with your dealership?