Most all of the soumack outlining in the feathers is structural Soumack which means it is done along a fell line even if it is an eccentric fell line.
The Roman numerals in the clock face is vertical soumack that floats passes and is only controlled by where ever the next warp is that I let the soumack jump to. This type of soumack doesn’t have to go vertically. It can go diagonally, horizontally or vertically. It can zig zag back and forth over a solid area of weaving. Not the example of the back and forth in the pale green area next to the dark soumack line which is a structural soumack.
The quills of the 3 women’s feathers are structural soumack that has had the soumack twiners graded in different sizes-less or more to create the shaping and thickness of the quills. Under these feathers is another area of soumack—the outline of the puzzle piece that is under the bottom feather. This outline is both structural and vertical.
In the horizontal direction the line is structural soumack running along the fell line and then turns and moves vertically over several over several passes to become vertical soumack. To a certain extinct the width and thickness of the line can be controlled by the amount of passes that the vertical soumack passes over between encircling the warps.