A few other comments...Lama Bear, we have gone to a 2 hook system on our aircraft to comply with Transport Canada's latest requirements for live sling loads. We use the ship's standard electrical/mechanical cargo hook, plus a second hydraulicaly releasable unit attached to the airframe for the rescue. The fixed line is Y'd to attached to each unit.
As you mentioned, the sling distance is kept to a minimum, then the patient is loaded INTO the aircraft for the flight to the hospital. unfortunately, no second aircraft is available for the transportation.
As you mentioned, the Vertical Reference aspect of the job is second nature to us, as well as yourself. We are operating on a 150' line almost every day here, and the commercial loads are generally 5 times what our 2 rescuers weigh.