A very interesting thread, and a worthy Techlog discussion
I cannot add much more in the way of wisdom, but perhaps can help simplify it or provide a 'take-away' point.
1. Decision maker's rule of thumb for attempting an Overweight (over MLW) landing:
"Is the hazard of continued flight, greater than the hazards of an overweight landing?"
The hazards of the overweight landing having been identified by FE Hoppy, JT and others. Especially the exponential increase in energy that must be absorbed by the gear and airframe on touchdown (Vg Max) and then dissipated via braking systems. Also, beware the temptation to overestimate one's capabilities to 'handle' an abnormal situation.
If you can't dump the fuel, and nobody is likely to die or be injured by your holding 1hr or 2 hrs --
hold.
2.
"Make fuel on the easy days. Not the tough days."
If your airline is like our airline, the focus on reducing carriage of 'discretionary' fuel and routinely uplifting Minimum Operational Requirement across the network, every day, will have more than offset your burning 4 (or 20) tonnes the one day you may be called to do that.
3. Overweight landings are different from 'not full factors' landings.
You may also be faced with the situation where you are at or below structural MLW, but forced to consider putting your aeroplane into a field that does not meet the 'full factors' 1.67 (dry) or 1.92 (wet).
In that case, you have eliminated one unknown - you will have landed your aircraft at that weight many times before. You are in familiar territory, handling-wise.
But halving the factor, is quartering the margin for error.
If, after considering the italicised advice, you need to put your aircraft onto a runway that has less than full factors, you have a situation that your cabin crew, your pax, and the airfield services ought to be briefed in on. The subsequent landing will not be pretty, braking may be forceful, and any handling error on your part might have you off the fairway and in the rough. Literally.
My 2c worth.
Great discussion.