Insufficient strength: You take a penalty equal to (required strength – current strength) to attack pools if you have insufficient strength for your weapon (default penalty is just -1). Same for armor. For a shield, its defense bonus does not apply if you have insufficient strength (though concealment vs. ranged weapons still does).
Initiative for two weapons or weapon/shield: The initiative penalty is (weapon 1 + weapon 2 – 1), where the total penalty can’t be better than either held item.
Ex: someone with a parma (-2) and hasta (-2) has -3 penalty (2+2-1). Someone with a parma (-2) and pugio (0) has -2 penalty because (2+0-1) is better than 2.