Silky: You may be very correct in your assessment, for using the "green Dot"speed,as an index of true weight of the aircraft for alt' changes.I've simply found that with the 'Actual'info at hand:temp,prog,perf',and variable cost index,one can get a better idea of the feasability of Climbing,or not(Its worked for me for eight years),
Cheers(up the Lord Darcy LBA)