If you do tip the tungsten, resist the urge to just keep going. Stop and swap tungstens or grid off the aluminum coating on the one you dipped. It will make a big difference. Also grind or brush off the area of the plate where it went poof, and remove all the black soot, or just move to a fresh area. Cleaning action will break up oxides, but not much more. If it doesn't look clean, it isn't. Aluminum and stainless both have to be squeaky clean to get great welds. Do the grind/brush, then the wipe down with acetone. Also if your rods have been sitting around give them a wipe, too. If the rag comes back dirty, do again until it doesn't. Aluminum oxidizes up instantly after you grind it. The cleaning action will take care of that, but anything more, you have to remove before you start.

Any idea of what your amperage was? Use a larger cup than you do for steel, and I would back down the flow like Sportbike said. A #8 will need about 7 lpm or so, more as you get bigger. I think tapping the pedal is a must or dial in some preflow. Either will do the same thing. You want to hear the argon flow settle down before the arc starts. How long that takes will depend on your setup. Usually just a second or so, but it's a sound thing, you can hear when the blast is gone and the flow is steady.

Maybe use a little less stickout, so you can have the edge of the cup touch the work before the tungsten hits the puddle. That will help guide your height and keep the dipping down. Be sure to have a good prop and arrange yourself to be able to hold the torch steady.