You need to build a boat with 4 props from each section. So 4 metal props, 4 wood props, 4 plastic props, and 4 (what other the other section is) props.
I'm not sure when you guys made this change but I didn't find it until I made a complaint on slack and someone told me how to fix it. This is a good feature but its not obvious that you can reconfigure that particular window unless someone tells you about it.