To the OP, I'm sorry to tell you this but you wont have much more viable information to your question. Not because of the thread derailment we are experiencing here, but more specifically because I spent a month searching for more information / data / RW experience about the capabilities of the truck in regards to towing, and found nothing around the 'net - including this website.
Most of the information I found was gathered from a string of PMs with a member here, who also owns a Prius. And no, it's not Hannibal. ;-) I bought the truck based on my own knowledge of electrical motors and systems, and this particular member's feed-back. Yes, it was a calculated gamble, and one that I'm quite pleased with.
This is why I wanted to eventually create my towing experience thread. Guess I never imagined it would have come to that low...