Hello BOAC,
Not sure what you mean exactly wrgds to, not knowing your F2 manoeuvre margin. You still have a pictorial representation of your manoeuvre margin on the Speed Tape, what more do you need? I'm probably being thick here. Can you elaborate a little more pls.
CAPTIJNS, with respect, your 40% setting may work well but wastes precious fuel over a long career not to mention additional noise. It doesn't come under the heading, efficient.
Rgds. IMLA