No, I don't think it is... you risk cracking/breaking the spoiler. A friend of mine needed a rack as well, and ended up getting a model-specific hitch & rack for his Prius. I have the Saris T-bones 3 and absolutely love it. It comes with a spare base (for when it's not on the hitch), and that doubles as my workstand.
It's super light, even my gf doesn't mind installing it!