Other than practicing and cleanliness , I find you got to be ready to move fast with a spool gun. I haven't had much luck on thinner sheet metal with the spool gun.
Probly will try to tack the pieces together and just have it tig welded , unless I stumble on the something.
I noticed the few times I messed with the spool gun, the alum. wire was dancing all over the weld area, I bought a roll of heavier wire , hoping it will help . Too dam cold out side to try anything now, but may set the pieces on my garage heater and preheat them some when I try it . -------more to come -----