I was talking about engine failure on final,followed by the decision to go-around. in this case,boeing recommends "follow the engine inop go/around proc" (fctm) wich says "use flap 1...."
In case of eng failure during go\around,indeed Boeing recommends using flap 15 (already set at GA).
80/20 I agree with you about the aerodynamics efect of retracting flap from 30 to 1 ,but I was told that from flap 15 to 1 the flap is designed to retract slow,so enaugh time to increase speed.
brgds Alex