Heroes of Alvena handles weapon sizes and those who wield them differently than the core rules.
Weapon Size Categories: The size of a weapon compared to a character's size determines whether for the character the weapon is light, one-handed, two-handed, or too large to use.
Light: If the weapon's size category is smaller than the character's, then the weapon is light for that character. Light weapons are easier to use in the off hand, and they can be used while grappling. A light weapon can be used in one hand. There is no special bonus when using such a weapon in two hands. A light weapon that is at least two size categories smaller than can be treated as a simple weapon with a range increment of 10 ft.
One-Handed: If the weapon's size category is the same as a character's, then the weapon is one-handed for that character. If a one-handed melee weapon is used two-handed, apply one and a half times the character's Strength bonus to damage (provided the character has a bonus).
Two-Handed: If the weapon's size category is one step larger than a character's, then the weapon is two-handed for that character. A two-handed melee weapon can be used effectively in two hands, and when damage is dealt with it, add one and a half times the character's Strength bonus to damage (provided the character has a bonus).
A character can use a two-handed projectile weapon (such as a bow or a crossbow) effectively in two hands. If the character has a penalty for low Strength, apply it to damage rolls when you use a bow or a sling. Add no Strength bonus to damage with a projectile weapon unless the weapon is a mighty composite shortbow or longbow.
Thrown weapons: Thrown weapons add the character's Strength bonus to damage. A creature can throw a one-handed or two-handed thrown weapon with two hands, adding 1-1/2 times their Strength modifier to its damage.
Ranged Weapons: Many ranged weapons require two hands to use effectively regardless of their size (such as bows). Crossbows can be fired one-handed if they are your size or smaller, but must be reloaded with two hands.
Too Large to Use: If the weapon's size category is two or more steps larger than a character's own, the weapon is too large for the character to use.
Weapon Size: Every weapon has a size category. This designation indicates the size of the creature for which the weapon was designed.
Unarmed Strikes: Unarmed strikes are based on the creature's own size category. Unarmed strikes are always treated as light weapons.