Thanks for all the replies guys, it's much appreciated.
I've taken on board all that's been put forward and read the other thread, but still can not establish a definitive answer.
The best endurance speed is DEFINITELY slightly behind the drag curve, not at Vmd. I don't know how to post a picture in the thread without a hosting site but the graphs I have are from Mr Boeing himself and are very similar to those posted in the linked thread above.
However, I believe Cwatters may be on to something:
I think there is a short answer to the original question. The units...
Fuel consumption is a measure of power (eg energy per second) where as drag is just a force.
To calculate a "power" from a "force" you have to multiply by velocity.
So in short fuel consumption is proportional to drag x velocity not just drag alone. It's the product that has to be minimised.
This seems the most plausible scenario, for my small brain anyway.
Unfortunatley, none of the technical pilots/TRE's in my current OR my previous company are able to offer an explanation as to why in straight and level, static cruise conditions the min fuel flow occurs with higher drag - only confirming that it IS true.
A long shot but I don't suppose anyone has an email address for someone technical at Boeing? I'm pretty sure if I email their customer helpline I won't get an appropriate response!
Thanks again guys, keep the suggestions rolling in!
TJQ.