As your son is on a 504, if the school applies for extended time, using the College Board dashboard, the likelihood of approval is much higher, especially for extended time.
We won't ask for extra time for this "practice" test. It will give us a good idea how he does without any such request and give us time to do so. I'm not likely to ask for a time extension for the PSAT. The writing part of the SAT is where I'm worried that time could affect things. I didn't request extra time for the CASHEE, nor does he ever need it for the state testing.
Do they give extra time for the PSAT? What about the SAT II? I was considering having my son take the Math2 & Chemistry test this spring.