Getting back to the original question it is interesting that photos show the Sikorsky R-4 doing ship trials being flown solo from the left seat. Other photos show the helo with a hoist on the left side, which meant the helo had to be flown from the right seat for the hoistee occupied the left seat once up at the door (Lateral C of G considerations aside). So maybe Sikorsky either set a convention by deciding on what side to put the hoist, or the side to put the hoist was dictated by the preference of seating position by the majority of pilots. Who knows?