I think both these pictures are believably
proportioned. This one on the right is the only one where I didn't put any elements in the background (the figure is actually sitting on a low wall) and I realise it therefore looks strange.
So, I added it in after the event (see below) though it would have been easier to do it at the time and I am not sure if the angle of the wall is correct.
10-minute drawings :
I used pencil here so the images are a bit feint to see. I think they are well proportioned. In all the drawings on this page, above and below, I judged the length of the head using my thumb against the drawing medium. I then used this measurement to judge the relative proportions of the rest of the body. Where the body wasn't standing upright, I still used the same theory - moving the measurement around the body even when it was twisted or sitting, imagining where things would be if it were stretched out straight. I did attempt to see the different parts of the body as more geometrical shapes, in order to be able to lay down the various shapes quickly. The background seat helped a lot, providing horizontal and vertical lines to work against. As I drew I judged where the bit I was drawing was in relation to everything around it, to ensure it was in the right place.