The first thirty-minute drawing looked successful to me for the first couple of days, until I started learning more about the proportions of the human figure. This was all done with outlines, so it has a bit more detail than my others. Since these drawings are based so strictly on realistic proportions, something I would suggest doing would be to flip one of your works upside-down and sideways. It's easy to get carried away and focus on details in the drawing and not think about proportions. Doing this will give you another perspective on the forms and lines. Try it out.
Now utilizing the frame-style of laying out the drawings, I found it easier to get the proportions correct. The form is stylized, but I think it's more of a lack of concentration than a stylistic choice. I really like how it turned out, but I wonder if I'm going to be teaching myself realistic proportions the wrong way, not that it's bad to stylize, but I figure I should learn how to do it right and then try a hand at exaggerating aspects of the human form.   

My last thirty-minute drawing was not as successful to me. It seems much easier to grasp proportions on a smaller scale. I find myself doing a lot of reworking on the frame. I should definitely spend most of my time doing that before I fill in the skin and muscle (which I know basically nothing of right now) I'm going to try to work hard on drawing the frame during these 30 minute sessions. I think it's important to learn the proportions and apply them to all scales, long before filling in the gaps.