I actually don't mind a fat model. Maybe you should then concentrate on drawing the negative shapes like in a Brague drawing. Having a model not showing you what you want to see is a challenge and by looking at it in a different way, you can bring that to future studies.
I too liked using pen for life drawing as it helped in concentrating the mind to getting it right first time, but then again I tended to scribble to get the form. It's when you're not bothered about producing a perfect rendition, your best work appears as you concentrate on the form first and foremost. Sod the structure - that'll gel later.
hey man, níce postures, but why don't you render one of them? would be awesome to see something colourful and not so scanned =)
you most defentitley are able to draw and know your perspective.