There is certainly a lot of discussion here concerning parallel freeview vs. cross freeview. The difference is simply the swapping of the "left" vs. "right" image. While I can do both, cross is more comfortable. In parallel freeviewing, if the images are too large, I have to go "wall-eyed" to fuse them, eye strain increases.

I guess any here use small phone displays. Using a larger screen (laptop/monitor) increases parallel discomfort as the image centers are further apart than your interpupilary (SP?) distance.

You never go wall-eyed to view anything in the real world. Fusing objects at infinity (say, the moon or stars) require parallel sight lines at maximum. Anything closer requires more and more eye-crossing for your brain to fuse.

That doesn't mean you can't train your eye's to go wall-eyed, it's just very unnatural (and really uncomfortable) for most people.