Back to previous comments on the ASA...
The option of buying the Axe version is quite costly (about £80 if i remember right? please correct me guys if it's wrong)
Another option is an external off/on ASA but this will add an EXTRA inch in-between your marker and tank making the distance from your shoulders to the trigger an inch further away. This is less costly (mine was £25 i think) and is the budget option. Personally I don't mind the extra distance but my tank is at least an inch shorter than your steely (mine is another steely, just a different manufacturer and design)
The Mrs runs exactly the same setup and doesn't mind the extra distance. It's all dependent on the size of the tank in the first place and personal preference.
a note on the external ASA though...it doesn't purge the mini. It merely stops the tank from releasing any more air by taking the pressure off of the pin on the tank. You will then need to 'dry fire' the remaining air inside the mini. It does make it easier to take the tank off the same as the on/off ASA though.
If the dough is plentiful go with the axe version. If not consider the external
(the external is not in my display pic, it was added after that was taken. That is my current tank though. If you want a pic of the external then just let me know.)