Cee,Confusing. I ask the dealer today. He gave me a number around 3,500 lbs. Sounds a lot better than 1,700 lb I saw some place. The small trailer at UHual is close to 1,000 lb empty.
I also put on a Rocky Mount TieRod forked mounted bike rack on the Porsche Bar today. It looked like it will work, alleluia! Thule said they don't have anything for this cross bar.
There are two tow ratings. The lower one you cited is for an unbraked trailer. The much higher number (which was 4500, now possibly higher) is for a trailer with brakes.
-V