Rule Monger: Cannon vs Mounted Characters

I love how the closest cannon crew member is
looking the wrong way. "They're behind you Doofus!"

This should probably be titled with the YATIMI8ED tag, but I didn't miss this. Everyone who ends up on the business end of a cannon seems to have though. Quite a few times now my opponent's disbelief has led to trawling the rule book for the tiny little sentence which covers what happens when cannons shoot at a monster with a rider.

In summary:
Cannon's are template weapons, they hit everything under the template, both the rider and the mount are hit simultaneously.

A Closer Look:


[p113] WHO'S BEEN HIT?
The bounce of  the cannonball is treated exactly like a special kind of  template, which we assume to be about the width of the cannonball itself. 

[p105] Templates: 
If you use a weapon or spell that uses a template against a monster mount, both the riders and the mount are automatically hit if the monster's base is touched by the template (note that this includes bouncing cannonballs!).

Pretty straight forward right? It is, right up until your foe decides to argue that the cannon would hit the monster mount first and then the rider - and only hit the rider if it kills the monster mount.
Argh? Where are the multiple snippets of rules which apply to this situation? You'll spend some time debating the first two rules, and if you're lucky you'll find the rest of the relevant pieces.

I think the cannon ball stopping at the mount (if it doesn't kill it) actually seems reasonable, but that's not how it works:

[p9] Templates: 
Some models, such as characters tiding chariots and monsters, might have several different locations that can normally be hit separately - in these cases a template is assumed to hit all the locations on the model.

In this case it helps if you think of the cannon ball actually being an artillery shell exploding on impact. The current dwarf cannon model actually has shells instead of the classic cannon ball. Unfortunately I don't know how to resolve this fluff wise as I can't see a shell bouncing through ranks of troops.

In conclusion, I'm afraid Mr.Non-Dwarf-Player, looking down the barrel of a cannon really is as bad as it seems for a monstrous mount and it's rider.

Let me finish by saying...