Adding the scaled scores is not how you get FSIQ. I believe you plug the sum of scaled scores into the WISC's proprietary scoring system to derive FSIQ. The scoring system is available only to testers. I do know that my DD's sum of scaled scores was a little over 10 points higher than her FSIQ if that's helpful.

Some posters on this board could tell you the FSIQ from the scaled scores. Maybe one of them will respond.