Hi,
You should not try to change the echo canceller settings in the linphonerc file on Android.
The ec_frame_size parameter has no effect with the WebRTC echo canceller because it only supports frame sizes of 80 and 160. Linphone forces it to 160.
With have a table of optimal configurations for some known devices (for example the Nexus 7) and if you use Linphone on one of these known devices, you will not be able to change this configuration.
Otherwise if the device is not known, you should run the echo canceller calibration from the settings to get the configuration corresponding to your device.
In your case, the Nexus 7 is known by Linphone (that's where the delay_ms of 170 comes from) but the Motorola Xoom is not known. Therefore you should run the echo canceller calibration on the Motorola Xoom device.
Cheers,
Ghislain