I have that antenna and as you can see it's mount on my truck mirror arm now for over 1.5 year and 84,000 miles. In speeds over 70 and a good cross wind it will move in circles and I'm sure it's good intertainment for fellow travelers seeing it. That spring will allow it to move some but not enough if it were mounted where you show it that if you hit a larger branch that it would flex enough not to damage the top portion of the antenna.
12v 500ah, 20 cells_ 4s5p (GBS LFMP battery system). 8 CTI 160 watt panels (1,280 watts)2s4p,Panels mounted flat. Magnum PT100 SCC, Magnum 3012 hybrid inverter, ME-ARC 50. Installed 4/2016 been on 24/7/365, daily 35-45% DOD 2,500+ partial cycles.