I too want to update my ISY-994i to 5.3.4 from 4.9.0 but I have a z-wave 300 dongle in it even though I have no z-wave devices. Since 5.3.4 is not compatible with the z-wave 300 dongle and the 500 dongle does not seem to be available, is there a way to remove the 300 dongle and safely update to 5.3.4? Is there a way to add a 5.3.4 compatible z-wave dongle? I have a very stable network of Insteon devices and don't really want to replace my ISY-994i at this time.