[edited] Parallel cameras - question about convergence?

The way the depth is perceived is through parallax. That separation of images is the parallax. The fact you are seeing to images means there is too much parallax and your eyes cannot fuse it. Even in they eyes are flipped they should still fuse. Are you sure the cameras are aligned properly? Be certain your cameras are parallel, they could have been deverged (both pointing away from eachother). Try taking them outside and align them to a far away building, this will affix them parallel.