I think you will find its far (FAR) less common for the extended iq to be calculated on the SB than the Wisc. My DD has a Fsiq in the dys range & multiple ceiling scores, but it certainly wasn't an option for her. I also know a child with a score half a standard deviation higher again, extended norms were actually discussed for them, but still not relevant. So you'd need to be WAY into DYS standards for it to be important I suspect.