I thought of this topic as I was just sitting in the garden and creating some cylinder hauling loops.
Simply putting cylinders into tackle bags and pulling them up a pitch is not safe. Cylinders are heavy and caving bags get a lot of wear and tear and the arse can fall out of the bottom of bags when you least expect it. Stitching can give way and your cylinder then goes into free fall - terrorizing and possibly injuring people below you - if it doesn't go bang!
The correct method is to make some loops from about 30cm of 4mm ish cord
(from a climbing shop or similar) and make a loop by tying a double fishermans knot in it.
Tidy the ends with a lighter and they are ready to go.
Next, larksfoot the loop around the cylinder neck and put a screwgate karabiner through it.
It is also strongly advised to put some steel Din inserts into the valves, as bashing them on rock on the way up a pitch will bend them and render them useless - It has been done plenty of times!!