I have a problem each time I make a change to my part factory. It is when I require a left hand version of the factory I create a mirror derived component. When there are changes required. I have to reestablish the link to the child part because all constraints and any additional features added to the derived part have lost all references. When multiplied by the number of different versions of that factory component and each different assembly. It renders the time I save by creating a factory component useless. If the mirror part was not a part factory - I rename the old parent part and the link is reestablished to the changed parent part when opening the derived component by selecting the changed parent. Also see "mirror sheet metal part factory option & qty override"