^TC, no need to waste your time. I have pictures of the cannons that I already uploaded into the gallery.
Toontown is currently using a version of panda that isn't out yet. I'm guessing POTCO is to, so accessing the phase files may not be possible at this point in time.
The skull cannon may not be a part of ship customization. I think it would make more sense for them to keep it exclusive to skeleton ships.
It may also be possible that the different cannon types can mean they're more powerful. I would think that the big heavy cannon would do a lot of damage.