Head Angles

Here's something I've been struggling with, these past few days as I've been drawing. Part of drawing humans is being able to draw from any angle, including above- and below-shots. Unfortunately, these are the hardest to draw as I have to consider facial feature placement, angles, and the dreaded space under the chin in the case of below views.

I know these aren't the most extreme of facial angles, but here are some examples. As for the first face, according to my reference sheet the nose and and mouth should be drawn closer together than in a straight-on face. It's hard to do that without making the mouth look too high. Another difficulty is the shape of the nose - if I try to draw the entire thing, it looks too long and sharp. So here I've resorted to just drawing a few lines to indicate that the nose actually exists.

In this second picture, the head isn't really angled up that high but for this kind of view and higher up, I now have to draw lines to separate the front of the chin from the bottom. If you would feel your chin for a moment, there is no definite "edge" to your chin - it smoothly curves to the bottom of your head. Unfortunately there is hardly a way to draw a smooth curve with lines, so it looks like the chin stops abruptly on the face.