Listened to this a few times now. Really a wonderful performance up there with the likes of Mordkovitch and Opitz (violin & piano there, I know but the musicality reminds of that recording).
I wonder how you managed the balance between the viola and piano? In the parts where the piano volume ceases and it recedes into the background - did you attain this in the mix or via live performance - or both maybe?
The balance was pretty good in the main pair, so didn't need to push the viola too much compared to the piano. It helps that I am the pianist, playing my own piano in a room that I know well;-) And of course the viola player is really amazing. She has such a varm, singing tone that really comes through in recording.