I don’t do the marks before glue up. I was just curious.
I wait til after cleanup(or mostly cleaned up) to put any marks. I guess I’m not confident enough in all the lams and glass staying perfect thru glue up.
I pull a string thru same as you, but only use a single strand of B50. If everything lines up, then I move forward. If something is off, then I put more marks at fades and midlimb to determine which tip I need to move to make everything align.