Parachutist Drift in Crete

[saracv3]

Starting over w Crete scenario #6 after a game hiatus. One unanswered question is that the Parachute Drop process is some what unclear. When dropping a stack of units in a hex, does one roll the die for each unit to drift or does one roll for the entire stack at one time?

Nihon Silks’ method appears to be different, and I don’t see any drop rules in the Airborne series. I haven’t looked at Invasion 1944.