The golden rule that I have always been taught is that after potting you should be able to pick up the plant, not supporting the pot and it should all come together as one. That is how tight it needs to be. Needless to say I cram the media in pretty tightly. You can prevent roots from breaking by soaking them for 4 or 5 minutes to make them rubbery. Don't worry about snapping roots because you should be repotting as the new ones are just breaking out of the new growth. Orchid roots are designed to be destroyed after only a brief period which is why they put out a fresh new set with every new growth.
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