Great work Chen!
Did you notice how critical some members get as soon as it comes to a subject like shooting guns?
Is this base for gaming purpose too? The shape of your base raises questions about this, though this looks better than the normal square bases needed for gaming.
Don't feel disturbed by the limited number of artillerymen allowed in gaming rules.
Many rulesets use only 2 men: very silly
Many sets use 4 which is still unlikely.
6 or 8 man comes closer to reality.
And it does not matter because the base of the whole crew&gun is what is used in the game. If rules require a maximum of 4 men you can always count the other men as dummy's when it comes to counting the losses of crewmen to get a piece out of action.
That is why I always add 6 to 8 gunners to one piece.