I'm having a problem with keeping a uniform stroke width on shapes using the expression below, I think it has something to do with the parented nulls.
I also tried just putting the shape path in an empty Group, moving the stroke below the group, and parenting the stroke of the shape. It works when I create a new comp and create new shapes, but not with the shape layers I already have in my main comp.
I've used the expression on the shapes in the yellow scene and on the window outlines in the blue scene, but not on the character in the blue scene. The window is all out of whack, and when the null scales down the lines in the orange scene they seem to go below 4px.