Additional Spiral Galaxies

I was looking through the galaxy generation files and I was wondering if it's possible to create three arm or five arm galaxies? It looks pretty straight for forward by just modifying the basic files, but I seem to recall reading that it wasn't possible to do that. Anyone know?

Are there any tools that exist that can create custom galaxies? I'd rather not have to hand craft it, so I'm kind of curious if there's any generated galaxy tools.