Hitbox

Setup

Configure the head bone

Open your .iaentitymodel model file with Blockbench.
Create a new bone, it can have any name.

Resize your hitbox.

{% hint style="warning" %}

XYZ position doesn't matter.
Only XY size matters, Z does not. This is a Minecraft limitation, it's how hitboxes work in the game. {% endhint %}

Rightclick on the bone and select "Bone Config"

Check the "Hitbox" option and press "Confirm".