Rear shackle angle

this chart is what I set our leaf springs up
Sliders or shackles
.

When at the track- sitting on the line- bring the "R"s up to load the chassis
the car will raise the rear- if set up like the chart
while under load, the shackle will arc sightly forward,

the more angle used will make a different shackle arc , causing the rear of the spring , to move upward toward the chassis,
and the rear of the car to squat and lose some of the cars reaction time