Calculated property+layer based on number of pieces in stack

Is there a property I can reference to change an image layer based on the number of pieces in a stack?

Specifically, as a way to get around Vassal’s inability to keep relative positions between pieces when changing facing of a selection of pieces, or to have stack offset be reflected by piece facing, I’m thinking of a zero offset stack with one piece in the stack designed to switch to a progressively bigger image the more pieces there are in the stack.

Nevermind, think I have this figured out now.