I used the Dive Unity plug-in and developed an app for iPhone & Android. I mostly tested on an iPhone 6 and everything worked fine (I didn't use the magnetic button, just the headtracking). We produced a custom cardboard and when they arrived I figured this version was small enough to be used with an iPhone 5 or 5S. But then I found a problem:
Only when I use an iPhone 5 or 5S the gravity pull doesn't work properly and I get an slightly tilted horizon which adds to nausea. Did anyone have the same problem? What causes this? Can I do something about it?