Thinner lines might look better, since they represent the demarcation between different rag-pieces. I wouldn't worry too much about getting the patchwork pattern to perfectly match the illustrations; as you said, the patches change over time.

Once you've sorted out the patches, you might want to consider what fabric goes on each; in the pic I posted, there are some striped, checked, and polka-dot patches. If you use solid colors while laying out the pattern (as you seem to be doing), then it will be a simple matter to use the Magic Wand tool in your paint program to select each patch and then paste a fabric texture into it.

When you imported the mask .obj, did you have the Percent-of-Standard-Figure-Size option checked in the Prop Import Options panel? The number to the right of that option represents how large the imported .obj will be. It defaults to 100%, which means it will be rescaled to about the same size as a typical Poser character (about five or six feet tall).