for instance if you did it on first action so you could hit someone with a 20 stress attack and then fall I might have it kill you or seriously limit your abilities.
I don't think a character could do that, though. When they choose how many shifts of power they want to summon up, I think they take the stress at that point, and would be Taken Out before they could even focus the power into a spell. Without taking Consequences, they could only summon up enough power to take them out that way, which would be their Physical Stress Track +1. If they take Consequences they can get up to that (Consequences) + (Stress Track) stress mark. Any more than that and, once again, they are Taken Out before they can cast.
And that's before the backlash. But Backlash is almost irrelevant at that point.
Am I getting this right, folks? 1: Choose Shifts of power, 2: Take Stress, 3: Roll Discipline, 4: Take backlash/Make Fallout?