15-18 inches from piano lid. I use covers on all of my pianos in my home and in the showroom. Because it keeps out the dust and oil in the air. When oil and dust get on the strings after a number of years the Bass Strings will start to lose their tone. And the oil and dust will also seep into the bushing of the Hammer Shank at the Flange and the sensitive parts of the Wippens.
This can cause your piano action to become sluggish. I have also found that my pianos in the showroom stay in tune longer when I keep them covered. I know you will love this cover. Reach out to me if you have any questions.