In reply to bouldery bits:
> The intention is that cereal is removed from the boxes.
We need to determine the structural strength of the specific cereal then; will a two meter head of pressure be enough to collapse the flakes, significantly improving the volume packing efficiency? Many flakes barely survive transport in their box, let alone under the crushing weight of two meters above them.
Pro tip - duck tape the drain hole first if you want them to ever speak to you again.