Ok, did some testing and the star shell does work in SH4. I was able to fire them and they light up and all just like in SH3. Here's how to do it (quick fix until I can figure out why the SS shell won't display):
in the data\Library\USSubParts are the deckguns for the subs. Edit the xxx.sim file via hex editor (or use S3D as you guys like to use) and replace the ID for the AA shell with the ID for the SS shell. Make sure to give it an amount like 0x10 (which would be 16 decimal) or something. Now when you click on the AA shell in your deckgun it will actually be the SS shell. Fire away and enjoy the sights
I'll look into why the SS shell won't display on the deckgun screen. I tried to make it display on the AA screen also with no luck :hmm: