Do you have speakers connected to the BS6500? If not, my current thought would be to set both BLCs in A.SLAVE mode, as they are only sources. Set the one connected to the BS6500 to map the desired experiences onto NL. In the other BLC, the one in the main MasterLink network, assign those to a logical command (avoiding the earlier mentioned conflicts, which is a bit the ‘pain’ with MasterLink).