Skylan seems to be preferred for Harbeth's. I ended up getting a pair and am very happy with them. They are custom made to 20" for the 7ES-3, but I had them cut to 18 inches for me. I think Harbeth recommends 15-21 inches depending on your seating position.
Noel is a great guy and terrific to deal with.
Noel is a great guy and terrific to deal with.