What is a rule of thumb for knowing how much supplies to provide per person?

Sometimes we may have as many as thirty people going to Guatemala. To reduce bulk, it would be better to send two 15-person kits rather than three 10-person kits.

I have looked at Adventure Medical Kits to get ideas but what I got out of this thread is that it is better to not make clones of their kits. What do I need to aim for in building a 15-person kit?

Jeanette Isabelle
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I'm not sure whose twisted idea it was to put hundreds of adolescents in underfunded schools run by people whose dreams were crushed years ago, but I admire the sadism. -- Wednesday Adams, Wednesday