I gotta add that there is an underlying dilemma in the thing:
downward-facing is a great idea, as mine usually are
https://www.youtube.com/watch?v=p1xPV_SHG-g
but the mirror and the camera needs be must to face each
other ...so which of the two should prevail? How about a
severely enclosed (forever garanteed vapor and condensation
free) inverted glass cylinder the walls of which are slanted
in exactly as the cited car's back window?