This does make me wonder if the shape of the Tesla's underbody (very flat [1]) is such that debris is more likely to make a direct rather than glancing impact. Perhaps Tesla should take a leaf out medieval armor design and add more contour to the bottom of their car so that it can shed impacts more successfully.

[1] http://media.ed.edmunds-media.com/non-make/fe/fe_9171228_600...