MIG welding with stanless or Aluminum,COVER(shield) GAS

[crossy]

I am well versed at nearly all types of materials that can be welded. HAD Nuclear and ASME quals in my heyday. That said, I had only used my home MIG machine for LIGHT fabrication and rust repair on carbon steel(LOTS of it,lol). I just bought a small spool of 304L stainless and want to TRY it on stainless exhaust. The Lincoln website(my new Machine is good,230v Hobart) recommends a tri gas mix with 90% Helium, their plan ‘B’ is a dual mix with 98% Argon. I have pure Argon already here for my portable, Chinese TIG machine. Has anyone tried 100% Argon on their MIG with stainless???, I understand that the Helium helps flatten the puddle, but I am not real concerned with a raised bead on the exhaust, only that it actually weklds the two pieces together, and doesn’t rust. how about Aluminum in the MIG like a 4043? Thanx- Crossy