All vent covers are approximately the same height. All automatic opening lids on high-powered fans are equipped with current sensing circuits that will automatically shut off the lift motor when an obstruction is encountered or the lid reaches the end of its travel. This is normal and will not cause excess wear or shorten the life of the fan.
The small amount that the lid does not open underneath a vent cover has no effect on the airflow. Our testing has shown that once the lid is open approximately 50% that the fan will achieve maximum airflow.
It is safe to install a FANMATE on any style high-powered fan.