There are now four pad choices for Avid Elixir/XX brakes: Sintered steel backed, Organic steel backed, Organic alloy backed and Semi Organic alloy backed. I know the sintered pads are the same as metallic and last longer, but are noisier. Organic are softer with quicker wear but less squeaking. But what is Semi-organic? Are they half-and-half, best of both worlds kind of thing? Avid says that XX’s should only be used with alloy backed organic pads because of heat dissipation problems of the magnesium calipers, yet Specialized specs the S-Works Stumpjumper and Epic with XX brakes and “alloy backed semi-metallic pads” (Specialized words). I assume Specialized is actually referring to Semi Organic alloy backed pads. Does this mean that the Semi Organic alloy backed pads are a better choice for the XX’s, even though Avis says only to use Organic alloy backed pads?