I'm in a game where I want my character to eventually build a cannon, and I'm talking to my DM about the prospect of putting the Sizing enchantment (from the D&D 3.5e Magic Item Compendium) on it for ease of transportation. As I thought about it, though, some possible rules complications came to mind: What happens to a siege engine's numbers if it's not at its default size?
Size-changing spells, like Enlarge Person, usually have the stipulation that projectiles return to their regular size once launched, and so deal their default damage - the Sizing enchantment doesn't specifically call it out, though. Either way, the situation could get iffy: If damage isn't affected, a pocket cannon deals full damage. If it is affected, you could tell it to turn Colossal and explode a mountain with it or something.
Do the crew requirements change for an oddly sized siege enge? Would a Huge cannon require Large crewmen instead of regular Medium ones (or twice as many Medium crewmen?). Does a character with ranks in Knowledge (Engineering), like with a regular siege engine, take no aiming penalties for leading the crew of a Colossal cannon?