@ulrik I think it's 'cos synth group has some voice handling functionality that silent synth lacks.
We can get around the need for the group by adding a voice manager to the original network:
HiseSnippet 2289.3oc6Zs0aaibEdnjGaKGm3jMtcytnEP.sEHKRhfHkDkzVfsxwWhEZ7kX4MMsuDLgbrEgoH4RRYa0EEXeq+BJ5q8s9ZequleB8s92n+BZ6YtPQRYIYYkXassKMfglKblu4Lmy24Lmg666ZPCBb8QJ4NrmGEorLtUOmv1q2lX4fZtARYdbHMHD87ddjf.pIRQI6KXsojaND+4e8qdNwl3XPiqBgdsqkA8kVcrBiqc+F+ZKa6sHlzCs5jn2kazzv0YcWa2t.NxhKh7HFmPNltKg0sLX.DaZZE552Jj.fAoL2ycM60ps6YNh9+Zq.q2YSYETQsfART8Vt1lLDypEsdaKay8iVuAHjxB6Gu5yJV8qh2wxzpe8wRg6yaHe7ajTdnjIM7xlBdpIgWwDvaHPRIAjlS.oGfaY3a4EF2BCO2A2zIj5eDAD6IghnuHk2iW2E5fSXgNjSna4CE5+BOVuXwmlG92W7KOpqiQnkqSdWmccCo6473uXoucobK8GVJ+fMczQCsM1z36ZaS8GZyrcZ+w8hO1oam2Q8eZ9SI1co86Hr7SKSwiVllbK2PrpSzQWmlNVg64QcFkh.RJpXxeIpfoOjK8uqT5eHgMYVfLdQL+2pHNfSpyaRBIHEJtpVgzOmt2S9M+NqpNddd5qyK2b8Zcq+F6e6V0DkOrp9ZO4nsauco9su2SJzUOrrnL7uidBanpKJiPecyMXSmDx.5gUjG0OzhIrT1fdJX+ITfxg2fFbRnqGuuc7bcXqUkEtzE34wKtedidwEZ13LKyv18q36NoQap0wsiM0e+wM7hDvMMY5v7gL+lNmRsAXB6BWTQGLwbM6ZSBSa2wHajM.JNoT1YZzNAVg8RRF8QyXbRg3Cv6aEZzd3XLyPvHroccfQIE1cwadzQTivX.NGdq2b8vWkb5WTL8eN9E1tuiXGKn.0S.ITAu0OU1b99smueGTGiSl+wj5jwahcxnjcbNUTmRmJyMy4TYR0ie3E1ZBtAs1Txj.l2Q.yUDzFQrFRqsAoRRhwcbcb8Z65XYjTO4.Znu0wGS8SEzhkmqMwejqr0BCgnPj07W7l6O03.pMkDjRmRzINh13Fj8WhjDy6u.qUNdJqOv6IwwUg2Qcx2sFmR0mhkhHvXL+LMM9ivQR0YBndeATW.u11az5.opO+22Tp9q20+zTzsaPMH8tPsorSPn+1eTZT7RJfxjcbaf37BCW+JJ+WazpaPXLo+2sZge16GhI2lFtvlCcJ2.tD0Z7DprbWoZcdtSlYOk46EgOwtvrG.WFy29mUkeqfkJiyrBv6EQWMqJBGaXwY+e6vhOvsankyw6P.xW3TT3c61oED2oAElcGGpM67rJYXm7TTtHqLSBzh5XxK7efGYiprxJxFUiZL4RL2goNJGOANReZhZb.By7rpoAVACDnclq8.sixIwSwWky+O+0Qz4y+81nyuEOHbprRkKBisr53MPr4eBPpeDoqc3GbDJWdD4vypWHh7+8euwKgSRR7u9hPPYhCmLQDB4+9aBLx9+MIvXbhnEwaddnOQcFb2SBMsaRncS3eqeRYQ6RCOy0+Dt0m72vAijQQF3EU0Z11tmwRvokTKlun30tuqcuHlG9Jk5Gv6wB3hEf+PhWKB9q0wsKKEoh0v1jfCIV1LWkPPgd.H2yoEzYtORPWTYWNYCdKhAHb6sOgkZzGfMhRqUAijQ8Fi238KlTlMHQNMExJ.Sc3YpkcAHYYsyj.YkylX3bCL.mvLEBzEldeZgDMe0lMl7vlddTJl2vJvylz64cACSAKXpZfxMcLomyrTeFK2tDeRGZHU5xMpDLU6X47ZQZywLIOZGx48KWFJ2Jj50x52yKqBkEW.EmMue+X0iRLnyGOnyi0ROp4fJfmTi7pvLqVT7nVtdQUUcfy+D5YBInnCZZ0qWrbEcMsRkqUsVE4ktrkO8a5B678hfyBXM9ThF0pTMEdlGqpOhk4x7AO+ALc2QuXGqDTcjRvW.V7idPm6xFT1fr.d+1Leso53UdTlmGFyfPI9pKPnD52KfIsMCFP099XpL5hBhVuRZ13jyE2YNqDPSlQbrOfIKg1aDL47.nVmwbSdHw+XZHOGXIqPdSLNTd7sAoKB8kgK1UgrB9TVvzusCwgvB5o+rwZbYLKl577vsSOeWX3QWUSzLIMQ2Dh41DBTVj7PPvj1lM2vMuFbaMGVc5rtTqWUuppdMU8xZUJoUR5HSFf2GlFVTpYDGbeRXMtdWVyi4I9JMC0sBRVPjykXpqREmJIbtnjijbmpxsyZJWTZPhvxCw5kJoUnJLR0KWRubkZkldcHQxNG4pbpHiuCN9DOiTS+iBMOePiipuOwURJ1AoiRQ09nXp1z85JQ4lIE0hxG5pLEG4ZcCc6.KZdhLR6GI4rhFKq+x3lAul0pAoOgALZSyMrOjKD8tXdvhIxJyJxZ3Yjo8Obqmyr4UIyO7AFbKe97T2y3Jh4+SwaS7MM.RGy3y0A.fgjOOts7wMleq2nNHmUz4HWBGzErpCHmg5HnE4LMDYtlD7RhR1hazRzASwsWsHtbYUV4fnKuZU7ypB9pXO0JVWSuhZopH+nDU8PrZEUguNc0hkpnVQGFpvtNRufZEKWUsrVoZ5LmW5ZHOVP2Ad9ThYzT6QbFnBl5AR4GwvZ4R0KVoJL100.+nfWxiiPUkBBPUQud4Z0pnU45gKXRRNPVrVhTCvUBDIFfGbZbdA3yqHq.xSVdgDQ9I3DJAV1gxuyjbXQgwwthPwGmSV4+7q9yMdURi8zIR7QMdUWh8.1ZxaS8C0N7Rx63bSHYwON9Lp2NYcLkI6RBj9YxOsjn7B2G2bH+Sh9vShZN9KPYJSfLBMz03WK+jIDBgSAe4hwMw2QADvRxis8rw84J8kC9kn7Qa2F8QTDlJwfYl0DgC9EMbsHBGuyUFovrcB5+LrjiIOOEQyzX8d3WcKAvahjReSLGcHF9tu0Pb8nLB0E40.qaG92CeN7Nrx4GxWfbGHv52ZXjdntvKpMsuXoo8EKOsuXko8E0m1Wr5z9h0t7WjctG4IVY1Fvgy2eSAmoxlNLBTtYB5+RI3Fhp
Lots of good information on this here.
If you ever figure out how to modulate parameters within a hardcoded network, please let me know! So far this has eluded me.