No worries mate!
John,
No worries mate! Long day for me so I'm kind of tired and can't find some of my reference material. Again much of this seems contradictory or illogical to a pilot. It did to me UNTIL I went through the training and work experience as a performance engineer.
If memory serves me well FAR 25 covers certification from the perspective we are discussing. This section imposes a number of restrictions (legal term conservatisms) on the testing process and results that are incorporated into the AFM. Why? To give a margin of safety and allow for aging and errors that creep in due to differences between pilots. A small sample of these are the effect of a headwind is halved but for a tailwind is doubled. The brake pads used are worn down by 80% (only 20% remaining).
Anyone who tries to say you can discuss performance without considering obstacles, 2nd segment is always the most limiting, or you can ignore special departures if the weather is not IMC is to be ignored. More later.
The better 7/8's is ringing the dinner bell!
More later dudes and dudettes!
Alternate forward CG is an AFM supplement that is airframe specific and must be purchased. Most manufacturers treat this information as proprietary and confidential so you would have to discuss this directly with Airbus, Boeing, or your manufacturer.