60 ft trouble

I would get someone to video the launch and slow the video down to see what is going on.
As an example, the tires may hit, rear unloads and tires spin; or tires spin immediately.
SS can handle 4.10
How many times have you had the car out? Could it have been track prep? Have the tires dried out?
moving the rear-end back took a ''small?'' amount of weight of the rear wheels .