The screen isn't the issue but the bezels. Shrink the bezels and 5.5" would be fine. As it stands it's a larger phone than some 5.7" screen devices like the Note 5.
Apple needs to get rid of the huge bezels and home button to make the Plus less ridiculous to carry. Then you could have 5" in the same size devices as the smaller one too.
Apple needs to get rid of the huge bezels and home button to make the Plus less ridiculous to carry. Then you could have 5" in the same size devices as the smaller one too.