I hold my phone with hand X, then tap with hand Y

This is one of my main complaints about the iPhone 5 screen: the iPhone 4S has a perfect screen size for my hands, where I can smoothly tap the "back" navigation button with my thumb if I hold it in my right hand. On the iPhone 5, it's near-impossible to do a smooth, single-handed tap on the back button without stretching (and I'm of average height).

The way I hold my phone, there's no "hard to touch" place (I keep it loose over my right hand fingers, though I use two hands when typing).

I asked my friends to hold theirs and touch all four corners of the screen. It seems that the top left corner is harder for all of them (they're all right-handed).

I find that there's a spot near the base of my thumb when holding with one hand that's hard to hit without worrying about dropping my phone.