The options you enable/disable in your custom mozconfig are '''appended''' to the existing config.
The default mozconfigs used for tryserver builds are available in Hg: [http://hg.mozilla.org/build/buildbot-configs/file/default/mozilla2/ http://hg.mozilla.org/build/buildbot-configs/file/default/mozilla2/]$platform/tryserver try ([http://hg.mozilla.org/build/buildbot-configs/file/default/mozilla2/linux/tryserver try linux example])
==Selecting specific platforms for try push==