As you said that is a tricky call. With so many factors one cannot isolate just this, or just that. However, it would be best to study math and logic or whatnot and come to whatever level you find high enough, whatever that may be and just for the duration of the experiment, then measure your IQ. At this point do not study to any higher of a level-of-difficulty in the mathematics, but you may continue applying what you do know, just don't do it as much as you IS. Than continuue ISing for about 20 hours and than remeasure your IQ. Any gains, while maybe not exclusively ISing, are likely to be mostly IS-related...that is all that I would like to see. Furthermore, if any of you feel up to it, the Prometheus Society has a giant online mega-test, which one can take. Supposedly they only accept people with IQ's above 164. You don't have to join, just take the test, and see how far you have come with (mostly) ISing. That would be a true test of the ceiling for IQ.