SoapUI enforce quoted-printable and adds equals (=) symbols

When sending a REST multypart POST request (~2000 characters Json string) with attached binary file (Image) SoapUI enforce the follwing:

1. Define the content transfer to : "quoted printable"
2. Cut to new line after 66 characters
3. Add "=" marks at the EOL

This obviously cause failure at the server side

Any advice?