It was possible to get 2X extended time on the SAT a few years ago but my understanding was that is only offered in extreme situations. On the other hand, if you think your DS will need 2X extended time in high school for all those standardized tests for college, then it may make sense to advocate for changes to his IEP now. However, taking 8 hours for a 4 hour test can be exhausting and have been known to create its own problems.