Wow, that's a scary project but interesting. If you're really brave and want to give it a go, the method I've learned and always used for properly softening aluminum is to use the acetylene torch with just the dirty acetylene burning and blacken the aluminum with it (make it sooty). Then turn on the oxygen for a proper flame and gently heat the aluminum until the soot just disappears (much more than that and it will crater on you) this should give you some workability with the aluminum. Maybe at this point I should put a legal disclaimer?