You will need to post a drawing or sketch of some kind -- I don't understand what you intend to convey with "L2 at vertical."
If the longest distance your gripper will be from the center is 25 centimeters, and the weight of your load plus the arm is 1 kg, then the holding torque of the L1 servo needs to be at least 25 kg.cm.
"stall torque" is the rating for an actuator/motor at which the motor stops and cannot produce any more torque. A motor that is held in stall for more than one or a few seconds is likely to destroy itself. When you see only one rating for a motor, it's usually the "stall torque," if you intend to apply continuous torque, the "working torque" of a motor will typically be 0.20 or 0.25 times the stall torque.
Thus, for a holding torque of 25 kg.cm, you may need a motor with stall torque rating of 125 kg.cm.