why would you want exactly 35%? Yes that will have ppo of 1.40 at 100ft but what's the reason of getting exactly 35%?
You got it exactly. it is my assumption that there is sand at 100fsw for 90% of the dives and to maximize the bottom time(min N2) at that depth and minimize the O2 load at 1.4 works out to 35%, however after reading the above posts I will be diving all 32% and not worrying about O2, and will deal with the N2 as it presents itself.
Happy diving, 12 days and counting.