I just bought a great accessory to haul the things that won't fit in my FRS, including my bikes!!! Check it out:
Flame away, but I'm just gonna say that the roof of the FRS/BRZ is super thin metal and not made to have ANY load placed on it. Just because you can doesn't mean you should...and in the words of the many internet garage gurus out there...Use the right tool for the job.