I have been burned a few times on new palm species that were reportedly as hardy as T. fortunei. I have heard that T. princeps is quite hardy though. I have seedling that haven't been tested yet. I can tell you that it is by far the most finicky Trachycarpus to grow. Very succeptable to over watering and root decay, and they don't seem to like very low humidity. I only grow them because of their great appearance. One day I would like to cross it with T. wagnerianus.
I also think WagxPrinceps would be cool.
Manipur and Nanus are not exactly easy to grow either,IME-
Princeps loves heat more than any other Trachy I have seen.
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From what I read on different forums, T.princeps is at least as hardy as T.fortunei or even more hardy when young.They are originally growing on the cliffs of 1600-2100m above the sea level, it is freezingly cold . As the locals told me there was heavy snow up to the knees in the stone gate area. It could be a hardy palm.
Plus, some more info supports the assumption as more people are growing them in USA or Europe.