Hi Merlin,
The Quads are used on stands, about 12" high, which looks a little too high but in practice works very well. One of the things we found is that the floor is as much a boundary as a wall and the bass really comes on when they are well away from it.
I bet you could have many happy hours adjusting those subs to blend seamlessly with the electrostatic bass, One thing that occurs to me is that if you use the original feet, the speaker would be very well decoupled from the subs. You could then experiment with tilt angle simply by putting rubber washers or whatever under the back foot. We found that they sounded best when absolutely straight rather than tilted back as they were used originally. This might vary with room and distance from the speakers however.