Player hitbox

How to change the player hitbox? I am doing a prone addon, but i not know how to change the places where the player hit. Like, i can do a sample prone, but when i use in small holes the player not will pass. Someone know how to change this to a small hitbox?

Bump. someone help please? i really need to change that

Not sure if this is it, but try it out

Player.SetHull
Player.SetHullDuck