I'd still be interested in having someone prove that there are sensors on the top of the roof. We know there are sensors in the door that impact the FaWD opening angles, but are they right on top where the rack would mount? If not, I'd be nervous about accidental openings (I have 3 kids) and the subsequent damage to the X and skis. It's not easy to find a picture of the FaWDs open without the roof piece in a completely vertical position.
Any owners willing to put a thin piece of cardboard up there on the roof and see if the FaWDs open?
Elon did tweet near the first deliveries that you could put stuff on a side of the Model X roof and the door would be disabled. Of course, tweeting something, and it actually being true is something that one should not count on until tested/verified.