I'd give a +4 bonus to your Reflex save, same as the bonus to AC for Total Defense.
The readying and moving could be useful to move behind cover, or move where he can't hit both you and an ally with the same fireball, but I agree with most here... the area is decided when the spell finishes.
The readying and moving could be useful to move behind cover, or move where he can't hit both you and an ally with the same fireball, but I agree with most here... the area is decided when the spell finishes.