Re-using 3D meshes in a file.
I'll provide the example.
http://www.mediafire.com/file/4afldw...sell2.dat/file
Look at this dat with S3D. Then look at how the actual 3D meshes were done. Notice there are very few actual meshes used to complete the Sea Forts. The Game engine renders the needed parts as we placed them. No need for extra meshes!
At 2+ MB as is? Doing everything as separate meshes would place it at over 9 or 10 MB!
(Yes. They suffer the dreaded Dynamic shadow stuff! I know better now.)