Ignoring the desire to have your feet in shot, do many professionals hang out of the door? I have done professional photography flights from an R44 (please let's not start an argument about the Robinson fleet) and happily been able to shoot out of the front and rear doors without obstruction from the aircraft. Clean shots, all whilst secured by the 3-point seat belt. The pilot put me where I needed to be to get the shots.
The only harness I have used was in a Navy Seaking where I did sit "feet out" to get the shots once the door had been slid open.