I just don't believe that it's good practice to use things such as high-pressure storage tanks as tools......that's all.
Why not tap out a curved piece of sheet metal on an o2 tank?
How about a piece of 3/8" rod?
How about a foot-long piece of 11 guage?
Where does one draw the line?
Or would it be better to simply NEVER use a high-pressure tank as an anvil/tool in the first place?