I have been using the T4 template in the payroll system. I created a new template by moving the T4 positions to where the T4A data is required. Note that I needed a new template for each code used in the T4A requirement. i.e. deathe benefit code 06, schaolarships o4, etc.
I have been doing this for many years now. My only problem is that CRA is nopw requiring me to submit electronically and that is a problem.