Jon Elson fired this volley in
:

Yes, and you'd want to set up a back-side shield-gas flood system, too.
Maybe a separate shield gas nozzle for the front side, too, and follow
along behind the welding torch.

Jon, all that's been discussed before in this thread.

Both sides of the work must be shielded until the Mg is well below yellow
heat, and that will involve either cabinet welding, or several nozzles.

LLoyd