The side pack allows you to have more room for items. Definetly, take it. It will be so helpful I can brag about it. With Claire, you can get it in the ship. With Chris, go through the door where you went to go get the Hemostatic for Rodrigo with Claire. Defeat the zombies. You don't want them in the way. Go up and it will be to your right. Make sure you put it on.