Thank you OS, there can be no greater accolade than that you would be prepared to sit beside me - either seat would do, I'm equally poor in both!!
The reason there are such quick replies is that I'm sure I speak for many when I say that we all follow your inputs re Perf A (and those of JT) with great interest - it is one of those subjects about which we should never stop learning and unfortunately the advent of the Airbus FOVE and other computer related systems can lead us to mere acceptance of figures without knowing exactly why they are as they are.
Must go and pack for my holiers
Cheers
mcdhu