Thank you for that excellent description, Nick. Reading it and thinking makes the hairs on the back of my neck stand on end.
One thing I wondered when reading Chickenhawk, and you've brought to mind. The helis picked up the troops from the PZ, dropped them off in the LZ and then (if I remember Chickenhawk correctly) returned to the PZ to wait until the troops needed extracting With very little cover there, weren't the gathered helis a prime target ? Or was it considered that the enemy would be so busy with the guys on the ground a short distance away, that they were unlikely to attack ?