Have used the ones described in "Essential Registry Terms" (http://wiki.gpii.net/index.php/Cloud4all_Testing:_Essential_Registry_Terms). Note that preferences' names are URL-like and the UIOptions model seems to be replacing dots "." with underscores "_", ending up with something like "http://registry_gpii_org/common/cursorSize" instead of "http://registry.gpii.org/common/cursorSize".