Like I said before - keep the car horizontal. Jack stands under the control arms or like shown - front tires on a buck.

Depending on the size of your [censored], add your weight to the driver seat doing any front end alignment, pinion angle setup, rear suspension preloads, weight bias setup.

There are plenty of YouTube videos of rear suspension dynamics from launch to the traps showing rear axle windup - I think DiZuster did a few.