Got my rack and and cargo box installed. To those who are interested in installing the Yakima Q-towers, most of the info you need has been covered covered by OP (thanks @
Nubbs). On thing I would add is to make sure you put some paint protection (I used the lamin-x roof rack protector) between the rack pads and your car to avoid getting those small scratches when dirt get in between the area.
To those interested in fitting a cargo box, the distance between the cross-bars is very short and neither Yakima or Thule made a cargo box that would fit that span. Fortunately, the guy at the rack place (Rack Solid) were able to find one that fit and was low profile enough to my liking (I went with the Inno Shadow 16). Worked great for some car camping new years day!