Your outer ear canal size has no relevance on your eustacian tube size. Tubes could be installed through eardrum to equalize pressure, but swimming, showering and such becomes a concern due to water getting into the inner ear. I had an eardrum rupture due to an infection, the rupture itself does not hurt, it is the pressure on the inside of the eardrum that hurts, and that's what you felt. If and when the eardrum ruptures, it may acctually feel like a relief, because now the pressure is equal. A squirt of Afrin prior to descent may also help open up the eustacians.