Does anyone have any Grandstream GXP2000's on 2talk and have sidetone working ok?

I can't see a setting in GXP config to turn on or off sidetone and the model is supposed to support sidetone.

GXP2000 firmware: Software Version:  Program-- 1.2.5.3    Bootloader-- 1.1.6.9



PS Just tried shouting in to the GXP and it does seem to be present but very low level, any ideas on changing sidetone level?