If the aluminum your thinking isn't just real thin have you thought about purchasing one of the many small spool guns for your mig outfit.
I got a really nice unit for my little Lincoln 140C that wasn't so cost prohibitive (does require a different gas though).
The spool gun for my Power Mig is quite a bit more, but with the 140C it's a whole lot more portable running on 120 volts.
Phil
I hear what you're saying but a tig setup is just so much nicer to work with. Esp when it comes to delicate little work. I've done small work on thin material where I used .030 stainless wire for filler rod.
You just can't beat a tig setup. Especially with a rheostat.
