No matter how much you carry, you'll always run out of something. You'll always need what you don't have. Friendly fire isn't. Your paintballs will bounce on him, his paintballs will break on you. The amount of cover you have in front of you is directly proportional to the chances of someone coming up behind you.
Incoming fire has the right of way.
Any plan, when explained by the team leader, will have as many different interpretations as there are players who have heard it. No plan survives Initial Contact. There is always someone better, faster, and younger than you. When you think that no one would be foolish enough to hide behind a particular object, a person will shoot at you from behind it. All things being equal, you really don't have a snowball's chance in hell.