Get organized with your friends
If you are traveling with several people, each of you will be carrying a suitcase, or at least you should. That means that if you are organized within the group, you can take advantage of all the available space so that no one has to leave anything behind.
Either because someone in the group has fewer things or is more organized, it never hurts to check among your friends to see if there is a place available to keep that item or garment that you could not put in your suitcase.