You didn't mention what machine you're welding with either. Depending upon the box, changing the frequency or AC Balance can effect your welds quite a bit too. Also, on thin tubing, setting the background pulse helps a lot to prevent blowout.
When you weld aluminum, it takes a bit of time for the filler metal to reach the same temperature as the base metal (3/32 rod to thin aluminum) so you may need to loiter over the puddle to get it to tie in. I tend to wait for the puddle to "keyhole" on the front then dip, travel and wait for the keyhole, then dip, etc. Once the base metal gets hot enough, you can dip and run like hell as the puddle flows really well. You might also lay your thin plate atop some thicker steel to help suck some heat out as you weld to prevent blowout (if you're having that problem).
Getting consistent beads requires equal travel to dip the entire length and those who can do it, are very experienced.
Personally, I find a Green tungsten to perform best on aluminum. It balls up perfectly and creates a very consistent arc.
