I want to override XenForo_Model_Avatar::gravatarExists which invokes XenForo_Helper_Http::getClient. There I have to add parameters for Zend Proxy. All is done in a new add on. I have written a listener with load_class_model, but infortunately extending XenForo_Model_Avatar does not work this way. I guess that's because 'gravatarExists' is a static method and therefore XenForo_Model_Avatar is not instantiated. Any suggestions how to solve this problem?