Nitoryuki

I know this is old but...anyways. I don't know how but it seems like the additional head parts are interlinked to the base head parts. So in my understanding, additional head part you added is linked to one of the base head parts, in order to delete them (Del key), you need to HIGHLIGHT the appropriate base head parts first by clicking it that corresponds to the additional head parts you want to remove, click that additional head part and hit del. This is pretty much what ZZjay meant.