Mold question

I made a plug for a modified rear bumper for my car. My question is, how many pieces do you thing I need to split the mold in to. The plug includes the part that is white plaster, the black diffuser at the bottom, the license and tailight surround up to the trunk lid, and the black sides from the original bumper. Also I’m wondering about separating the mold from the diffuser fins at the bottom. Thanks