If I am understanding your approach and my math is correct, a 0.25mL reduction per day would equate to a taper rate of about 6% over 28 days; a 0.5mL reduction per day over 28 days would be about 12%.
Given your history, you might want to consider keeping your taper rate at 10% or less for the first month to see how you respond. Reducing 0.4mL per day for 28 days would equate to a taper rate of about 9%.
Generally speaking, it easier to speed up a ‘too slow’ taper that is going well than it is to slow down and recover from a too fast taper.
