When you get to the point the spring has lost its arch, you are on the backside of things.... Unless it is softened and done
Correctly to a new "spring temper' it is hardly worth the bother...... We used to " rebend" them years ago, with them usually just relaxing right back; or snapping off in the back but maybe you will have better luck. To recreate a spring temper' after you soften it to re arch it, you will need to " overharden it" first then draw it back to a " spring temper'.......good luck with that.
I think I would simply buy a new Pawnee Spring and save the bottom of your rudder????
Best of Luck
E