The WISC-V is the primary instrument, which generates the FSIQ (overall composite) and the GAI (reasoning only, without measures of speed and memory), typically preferred for GT determinations. Also lots of other possible indices, which we don't need to get into at this moment.
The WISC-V Integrated is a supplemental neuropsychological instrument which generates a variety of clinical data, and some additional index scores, but not the composites that schools would want for admissions exams or GT placement.
Two hours is typically sufficient for a pure IQ and its associated reporting, as the average student takes just about one hour to complete the core subtests of the WISC-V. OTOH, in suspected GT cases, I would prefer to leave a bit more time, as these tend to take longer on untimed tasks, as students complete more items before reaching a discontinue point. I would not expect him, however, to stop testing, or rush testing, in the event that your DC takes longer than the expected one hour, so I doubt there will be negative effects on the accuracy of the results. Just be prepared to make additional appointments, or have the original testing appointment run over. Unless the travel requirements are excessively burdensome, this should result in little more than minor inconvenience.
