Yep it works just fine. I have been modding the game my copying some ships from other styles.
Such as giving the Arceans style "6" made from a copied selection of the other models. Just done this by copying all of one ship design cargo hull, and renaming the S1 to S6 for example. It should work in theory for new models too, just keep the naming convention the same way as the other styles.
However, bare some things in mind:
- Style 5 is actually the Dread Lord hull, so you can't replace that!
- In order to use the styles, you need to set the race files in My Documents/GalCiv2/Ships to use that style number. The game also has a habit of overwriting this, because the style will NOT show in the "Appearance" tab of the race in-game, although the model will be right if you don't use that tab. I have set all the race files to read-only just to be sure.
- In order to get the AI to use them, you need to do the same as above but change the file RaceConfing.xml in the Galactic Civilizations 2\Data\English directory. Of course, backup first!
- If you create new styles, any custom ships you save in them in the Shipbuilder are deleted every time you start the game. You can get by this by setting the files in you My Documents/GalCiv2/Ships folder to read-only.