Never used it to slow down, but that seems like a fair way to use it. Drives me crazy when i fly with people who have some reason they're rushing home and do everything they can to shave off a minute here or a minute there. Puts everyone on edge the whole day, risk taking increases massively, pressure on the other person to do something they're not comfortable with goes up, etc etc. and what do they achieve? arriving at home base 3 minutes ahead of the original time? great. well done. good for you. glad we almost flew an unstable approach for that.