Common house rules?

[Narwan]

Afaik the 10% arty rule came from the WaW family of games were artillery tended to be too powerful in larger quantities. It was a common understanding but not a 'house' rule for those games. For the CAMO games arty has never been considered a real problem (the occasional debate notwithstanding).
Though you might want to look out for games where one side has cluster ammo for the arty available and the other hasn't. Especially in combo with ammo units to keep the cluster rounds coming it can unbalance a game.

Narwan