Halo 3 Marnie and Halo 3 Master Chief helmets are the same size 10 inches tall, height. I bought halo 3 master chief is 2 part of plastic, hot glue in the middle. I'm seeing the sizing by both helmets.
Yesterday I made the back parts from Andrew DFT. Looking pretty good. I got a long back and small shoulders. showing different side views of the part. hopefully the straps and buckles hold it down into place.