If you want aluminum for its light weight, go with an ETI Fuecel carbon kevlar tank. I sacrificed a stock EFI tank to have one made, so he should be able to supply you one without having to send him your stock tank. Price is about the same, and the weight savings is about eight and a half pounds - one of the best bang-for-buck ways to lose a lot of weight besides a lithium battery. It's not a carbon tank, though - there's no carbon weave, so it needs to be painted.
http://www.eti-fuelcel.comThe site says he only has carb'ed tanks, but that's not the case. Lots of people have them on their race bikes, but as far as I know, only I and Kopfjager have them on their monsters. I think he's happy with his, and I know I'm happy with mine. Losing that much weight that high up really makes a difference in the way the bike handles.