ROS Effort control for RH-P12-RN(A) with OpenMANIPULATOR-P in Position control mode


I am using an OpenManipulator-P with a RH-P12-RN(A) attached. I am controlling the arm and gripper through ROS using Moveit. Currently everything is controlled through the PositionInterface but I would like to control the gripper thorugh the EffortInterface instead.
I tried a lot to configure it this way but cannot manage to make it work. I tried to configure the ROS controller as EffortController, changed the motors control mode in DynamixelWizard to Current and tried to change the hardware_interface to effort via the launch script.

Maybe someone was successful in configuring it this way or could help me out.

Thanks in advance!

@RobotisCommunity any idea ?