hi micheal

Yup you've you've understood right. Although in later examples which someone posted, the one with a hole in a plate, strictly speaking the thick thin lifework work would be as my image.

As for naked edges, thats down to the illustrators own interpretation so if it could be in its own style for easy selecting it would be a bonus, otherwise for me it would be enough just to be a thin line.

no to worry with the overall shape. I notice even in isodraw that the overall all fill (they call it a contour) is a bit rough but as it is lying under a thick silhouette lie its usually covered.

Matt