I haven't actually received my scion yet, but on my last car I just found a nice spot in the frame and drilled a hole in it, make sure to sand off any paint as well to get a good solid connection.
From what I've read from another thread is that they used the area where the seats bolt into the car, you could always give that a try if it's in the area.
From what I've read from another thread is that they used the area where the seats bolt into the car, you could always give that a try if it's in the area.