If you have two leafs below the main leaf, in front of the axle, clamp them both.
Take a real good look at the front segment. If there is ANY SIGN! That the main leaf is flat or bending in the opposite direction, Clamp it there as well!
They can be made out of mild steel but need to be 1/4" thick X 1-5/8" X 4-3/8". bolt hole spacing aprox 3-1/8". 1/2" fine thread bolts,2-1/2" long. (grade 5 is good enough). This is spec i got off of a old MMP clamps, that i will us to build new one for my car! After i get a few other thing done on my car.