I must be a simpleton, I was under the impression that when given 160/4 that meant we reduce to this as we can, i.e. as succinctly as possible.
What still truly baffles me is the amount of guys who bitch and moan about ATC speed requirements....and do their own thing...rather than a simple "unable...we require 170/5 etc etc"
I see very senior and junior 777 guys in equal measure struggle with this concept..the concept that whilst we all work together, ATC exist to provide aircraft a service within the regulatory and airspace framework.
Guys if you can't make the speed, just fecking tell them! "UNABLE"