I've got an Alcoa, too. I initially replaced the mishmash of old strings with weed whackers, thinking that something non-metallic and low tension would soften the "pingy" sound of the aluminum body. This was a disaster -- the strings had as much volume/tone/attack as limp noodles.
Currently, the bass is strung with D'Addario Helicore Pizzicatos. ( http://bit.ly/belwtY
) Bob Gollihur describes them as being similar to Spirocores, but they're cheaper, so I gave them a go. I can't say I love the sound -- there's definitely still a metallic character to the tone -- but I don't know if that's due to the strings or is just a characteristic of aluminum basses in general. They are loud, at least!
Because this isn't my main bass, I probably won't spend more time/money experimenting on strings for the time being. I look forward to hearing your and others thoughts/experiences.