3 up front in a 500 series helicopters is extemely uncomfortable and arguably unsafe as it is too tight to allow for freedom of movement of the cyclic because your arm gets wedged up against the middle passenger. the only way around this is to contort your wrist so your hand is almost in front of the cyclic (very uncomfortable and also arguably unsafe) or only allow kate moss sized pax in the middle seat. the choice is yours
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3 pax total is the only way to go, especially during colder seasons as heavier coats make a huge difference in such a small space.