finding no joy in a Google search
No need to copy --- Take a deep breathe -- clear your mind -- -- put your ruler and calipers away -- forget everything you've heard about guitar design. Then ---
Google 12 string guitar images, there will 1000's, use your imagination and draw a bridge that you like and is pleasing to you. Surely you can estimate that the second row of pins is about 3/8" +/- behind the first and a twelve string bridge should be that much wider than a six string.
You will find "real joy" when your own creativity is the basis of your work.