I was looking at the Transfer 3 website and Küat says clearly, "the Transfer 3 cannot be used on Class 1 hitches". eTrailer also says the Transfer 3 is compatible with Class 2-3, but not Class 1.
I assume this is because of the weight of the rack (20lbs more than Transfer 2), the extra bike, and the leverage of having a third bike farther from the car/hitch.
How has it been working for you, since you've had it longer? Worried about bending or breaking anything?