OPINION: Two piece mold or one piece

Need an opinion from people experienced with mold making. I misplaced this part earlier and after finding it decided to make a mold of it since it was so complicated to make in the first place. I was originally going to do a two piece mold, but then realized I don't need anything on the underside. My only issue is filling the void in the piece if I do decide to cast it. Any thoughts would be appreciated. TIA

If weight or extra resin for casting is a non issue, then a one part mold (with an open back) is way easier than a complex 2 part mold and registration points.

One Piece

I don't know what this is, so only you know what it is supposed to do. If it doesn't need to be hollow in the back, then just cast it solid, or cast in multiple layers of thickened material and brush in the material.

One piece it is then. Thanks guys.