There is a rather long thread on this forum about light trailer hitches for the Clarity PHEV:
"
Clarity - Any ideas on a bike Rack?"
But as is apparent from the title, the focus there is on a bike rack mounted on a light trailer hitch. The beginning of the discussion predates the TorkLift hitch, and includes the development and eventual marketing of that hitch.
However, so far as I can recall from discussion there, nobody had reported actually towing a trailer with such a hitch. I think there were some questions from those thinking about using it to tow a light trailer, but not anyone reporting they had actually done so.
My own experience with 3rd party hitches going back to the 1960s, is that just about any car can be used for towing. In fact, my father even used his classic VW Beetle for light towing -- altho I certainly wouldn't recommend it!
Frankly, it puzzles me that there is such reluctance these days about mounting a trailer hitch on a car and using it to tow a small trailer. Yes, you should take care when doing so, and ideally you should have some experience with how to maneuver while pulling a trailer before setting out on a journey. And yes, if you use a hitch on a car that's not rated for towing, and the car is damaged in an accident due to towing, then your car's warranty may not cover the damage. But your car insurance should cover it, so I am rather puzzled at what appears to be extreme reluctance to do so.
Of course, that's just my opinion, and obviously I'm not going to be the one to pay for any damage that you might have if you do have an accident. But Americans can and do use 3rd party hitches on just about any and every car made to tow trailers. Heck, even touring motorcycles sometimes pull small trailers!
Anyway... I don't think anybody on this forum has experience using the TorkLift hitch for towing, but if I were you, I'd certainly check that out to see if TorkLift actually recommends towing with the larger of the two sizes -- I think that's the two-inch hitch? -- or if it's only intended for mounting a bike rack.
Alternatively, as I recall from the same discussion thread, U-Haul said they would install a custom hitch on a Clarity... but I don't know how much they would charge for that.
She is spoiled from driving CR-Vs, a Pilot and now an MDX. She likes being high up. I actually love the newer MDXs and considered getting one but the MPG is a killer for the miles I drive. The newest MDXs average in the low to mid 20s which isn't bad but far from good for the miles I drive. She doesn't drive much so we can live with the MPG her 2007 gets. I drive 20k+ a year so the Clarity is a much better fit for me. 
