I had reason to talk with SBC about my adjustable slave a few months ago and they said that there is a shim on it that can be removed to give a bit more throw if needed. Turned out that I didn't need to do this, so I didn't look into it, but maybe if your setup has the same thing that would help.
Could also be that the pressure plate isn't screwed in properly. That was actually what my problem was. Sheared 3 of the bolts holding it in, so it was in constant contact with the disc. If it wasn't tightened down enough or somehow put in just a wee bit off, that could be your problem, too