Im a devout coward too John believe me! Even if everything looks right Ill take note of any involuntary sphincter-muscle activity I might have. As a captain I cover my @ss, but my ever-cautious cr@p-shooter has covered ME many times in return!
Yes for each critical airfield we build in the flap 40 fudge factors (x 1.67 dry, and the x 1.15 of that 1.67 dist for wet). In the Dry months therefore we can increase payload and/or fuel carried. I then x-check them with the old (large-sheeted) 23.10 Landing Performance FLL graph. I then take the
lower of the 2 weights should a diference exist.
The problem is that with the very short runways we operate into we cant use the flap 15 landing weight as a basis for commercial payload. If we did we could only carry about 4 or 5 bums down the back and a few slabs.
Our sim checks will include a sudden power loss or fire at low altitude and conducted at least once every 18 months. FAIL the exercise and youve blown the whole check. As a sim-checker myself once, I noted that pilot problems were exaserbated with low engine power settings (high and fast), so loss of thrust is not imediateley apparent. Thats why I emphasised till I was blue in the face the correct stable slot must be attained absolutley no later than 500 ft AGL, and the PNF keeps a good eye on the engine clocks as well.
Of course John your correct when you say there is no "right" answer and a lot depends on the particular circumstances of the day. I can easily mention scenarios where the QRH unfactored figure is all youve got to survive. Factor it and decide its too short and your a dead duck.