JW411,
the Hercules initially carried LOX on an SSP (Supplies Stressed Platform) rigged as you describe for airdrop. When the SSP was withdrawn from service we just carried it on a standard pallet without the airdrop option. Once had a fire under the flight deck on a trip from Patrick AFB to Belize when carrying 500 US gallon LOX tank. Made for an interesting few minutes.
As I recall we carried Avpin in 44 gallon drums under the dangerous cargo regulations.
I worked on Javelins, Hunters and Lightnings as groundcrew so I was serial Avpin inhaler. It is a wonder that any of us ex groundcrew have any lungs left !