Not sure for newer gen. Ninja.. but for motorcycles in general, I like to place the GPS right over the speedo display, since GPS gives more accurate speed anyway.
The central location of the GPS in-line with the moving direction of the bike would require less time for rider to switch focus of vision.
The less time eye spent off the direction of travel, the less reaction time required when something occurs.
With my 12 yr. ild GPS unit that's been mounted on over 40 different motorcycles, here's how I mount if on my pre-gen Ninja:
Simple RAM mount on the handlebar bolt:
