I think they are somewhat height sensitive, as most speakers are. The treble balance and depth perspective change some with height, so it's worth experimenting. But 20" seems to be the near-universal recommendation for the 7ES.
The Skylan stands from Canada have gained some popularity for Harbeths and are what I'm thinking of getting.
The Skylan stands from Canada have gained some popularity for Harbeths and are what I'm thinking of getting.