prefill_data for Creator + Merge & Sign

prefill_data for Creator + Merge & Sign

Hello,

Is there an option to use prefill_data for signer fields from creator? I see the option for CRM but it will not work with creator? I have tried passing the value in the signer data, and that also does not work.

Alternatively, is there a way to make a fillable field transfer over to Sign that is not read only? 

Thanks
James