Just a further follow up:
I now have good success using 1/16" tungsten on pieces this size, clamped tightly to start, using up to 135 Amps rapidly to start and then backing way off as the puddle forms and the part heats up. Breakthrough for me!

Thank you for these great tips! I never would have thought that I needed even more heat to start the puddle but that was key to my problem!
Now I just have to learn how much to back off before I melt the entire piece!

Trying to weld 5mm aluminum and am doing something wrong: Lincoln Electric Tig200 Square Wave machine AC 150 Amps Pulse OFF balance 60% Freq 100 Gas: Argon 18CFH 3/32" 1.5% Lanthanated Tungsten slightly rounded tip (with diamond grinding wheel.) 3/32" 4043 filler rod (which never actually ...