they more than likely have the light vest because the default isnt going to increase speed(except for the mobility of the gun) and the heavy slows you down...and i usually use it stock but if i add anything its a clip or scope(i dont really rember if you can add a scope i think you can) but use the light vest if you want to be fast but rember that your armor is going to go down and i use the gun as is for the most part...