Wearality Sky smartphone HMD review

First of all, I like this device a lot. This, plus a good phone, plus a good app, and it's almost Oculus Rift DK2 quality. I was pretty surprised by that. If you're considering getting Google Cardboard or Wearality Sky, get the Sky.

But...

But...

I was never able to replicate the calculation for the 150 deg FOV claim that Wearality makes. My calculations say, for a 6" screen, the arms being 2.5" (I measured them from the 3D model as well as with a ruler), plus a 1/4 to 1/2 inch distance to the eye, you only get 95 to 100 deg FOV.

Better than Google Cardboard, but not 150 deg. This is DK2 range. That's bared out by the fact that apps with which I'm very familiar on the DK2 look pretty similar with the Sky.

I'd really like to know how Wearality calculates FOV. Because for how I know how to calculate FOV [0], for 2.75" from eye to display, you'll need over 20" of display to make 150 degrees.

[0] https://dl.dropboxusercontent.com/u/9161524/fov.jpg