Thank you Andrew.
Please correct me if I am wrong:
At the track (medium bite asphalt), the car started with zero droop, the main chassis and the rear bottom pod plate level level. The car had no traction, can't even run straight.
Then,
I lengthen the center shock to have some rear droop. The car instantly felt much better, and drove easy.
I then further removed some shims from the king pins to have some front droop. The car felt very confident throughout the track.
Is this the correct way to gain rear traction for 1/12 pan cars?
Thanks again!