I think you just need to select MD1 as your connection in the Meridian config tool when you set up the connection from the 598 to the 861.

861v4/ID40, G98, UHD722, Mark and Levinson No. 29, 2 * Linn LK85, Linn LP12, Musical Fidelity X-LPS v3, Empire Vandenhul MC1000, NVidia shield, PS4, Thiel CS2.4, Thiel 1.6 rear, Audio physic Celcius centre, Rel Quake Sub