balance control after modifying some part

[luthfai]

The online_walking_module are using balance_control instead off simple gyro balancing like the walking module, i just modified my OP3 like bigger battery and adding new arm servo that makes the robot not balancing well anymore. Which part of the module that i should change to make the balance control works like normal again? and is there any documentation about the online_walking_module that explains all the parameters ? or maybe some external resource that i can use to learn the balancing algorithm that is used in this robot ? also i've read that it's possible to add ft sensor on OP3 because balance control is simplified from thormang3 can you explains it more about it ?