Aluminum is easy enough to weld for those qualified to do so. This looks like a through wall crack and welding it would entail complete removal and rewelding. This will affect the inner bore and unless you are prepared to deal with refit problems it won't be worth it. I am a former aluminum welder and currently a metallurgical, welding and pressure vessel inspector. You were fortunate to have such a great LBS and Specialized stood by their product. Chunk it.