Crab, "I think you'll find the hoist manufacturers were actually responsible for creating and introducing the twin hoist."
dear crab, you are not thinking at all. the dual hoist came about from the Cullen report after the MV Green Lily incident, were a very brave winchman was lost. for you to ignore this fact is an insult to the memory of Bill Deacon and puts you lower in my estimation than you already are.