I am having a lot of echo and audio problems with my handsets. In my experience with asterisk and aastra setting the sidetone gain sometimes help.

I know the Aastra phones support setting the audio gain for the the headset and speakerphone.
there are several options such as:
handset tx gain: -10 to +10
headset sidetone gain: -10 to +10
handset sidetone gain: -10 to +10
these options are usually in the aastra.cfg files and cannot be set using the web GUI.

How do I change these setting on my epygi quadro 8ml ? I have looked at the custom templates but these options are missing. Is there any way to edit the generated mac.cfg files ? Please note that I am not referring to the settings for gain control for the line settings but setting the sip settings on the actual handset.