My information on the SM tire was incorrect.

From Rodney Perry at Appalachian Tire (and Rodney is all-knowing when it comes to Hoosiers, and race tires in general really)...
The SM Hoosier is the same tire as the rest of the 04 Hoosiers, just at a reduced cost. All other information that has been widely spread by multiple groups about it being a different compound is incorrect.
It was simply an effort by Hoosier to get into the SM market, which seems to have failed in many regions.

As for the SM drivers from the ARRC saying the SM Hoosier was only slightly faster than the Toyo... I can now only assume that there was some sand bagging going on to try to get it approved. Either that or the Toyo does actually work as well as the Hoosier on a SM chassis. On an ITA CRX (for example), the Hoosier 04 appears to be significantly faster than both the 03 Hoosier and the Toyo.

I dunno... All I know is if I ran 205/50/15 tires I'd be stockpiling these at $142 each.