If you want to keep minimum clean, and that speed is slightly above 220kts, then just tell us and we will 99% of the time have no problems with you flying slightly faster. As a standard, we are now told to instruct 744's to fly at minimum clean as opposed to 220kts, as they generally have a min clean speed of between 220 and 230kts.
I was always taught that 777-300s also had a slightly higher min clean speed, so as long as I remember, I generally always give them 230kts instead of 220.