I remember the 160/4 miles being standard at the OLD Singapore airport back in the early 1980's but we were flying 737-200's then before the rudder scares and the Flap 10 (Gear UP ) speed was 160. Unfortunately since the rudder scares our effective min GR UP speed is 170 and I would be failed on a line check for flying anything slower! I take the point regarding the 10 knot tolerance but when one is told " Change Director call-sign only!" it does not seem to be the time to add any speed requests in the initial call! The result of this will be more gear down flying on approach with a ten knot overspeed for Flap 15 (737-300) to achieve the 160 knots to 4D.