Thanks Chris. I wasn't able to get it working with what you suggested but I did end up just adding the new model under the root and disabled the old animator, SMR etc. Doing that seems to work for me.
Hi Chris,
Thanks for assisting much appreciated!
I'm on version 2020.3.20f1 of Unity and the latest version of AC v1.74.2. I've sent you a DM with the package. Please let me know if you have issues with opening it.