I'm designing a flexible circuit that is little more than a glorified
ribbon cable, but nothing "off-the-shelf" will work. (So it is just a
single layer of conductors on polyimide with a coverlayer, but no tooling
holes or any other features).

Our first prototypes came back with the conductors off-center from the
board outline. I can't find anything in IPC-6013 that addresses the
relationship of the circuit pattern to the board outline, but it definitely
has to be tighter than a typical rigid board.

Is the "pattern-to-board-outline" relationship covered anywhere else?
Do I have to add some kind of note or dimension to keep the pattern
"centered" in the outline?