setCustomHitbox

public abstract boolean setCustomHitbox(Entity entity, float width, float height, boolean fixed)

Sets a custom hitbox size for an entity

entity

The entity whose hitbox is about to get resized

width

Width of the hitbox. Sets the X and Z axis at the same time, that's a Minecraft limitation

height

The height of the hitbox, has to be lower than 64.

fixed

Whether the hitbox can scale