It would appear at some point that the following class names can no longer be slung from any helicopter:
cargonet_01_box_f
cargonet_01_barrels_f
B_cargonet_01_ammo_f
I_cargonet_01_ammo_f
O_cargonet_01_ammo_f

These were objects that were originally capable of being carried by most medium and heavy helicopters. {F26602}