Upload & Sell: Off
As I am the DOBBIE in question (and Yakim , I am a free elf now ) I have made my choice.
I'm going to be getting a 70-200/2.8 mk2 but NOT if I can at all help it at the expense of my 100-400 .
It seems that under certain circumstances the combo could equal(or at leaste be close) to the 100-400 but it also seems that it needs the mk3 TC to be able to do the job. And as the mk3 TC costs well over half of what I could sell my 100-400 for it seems there is little point in sacrificing the 100-400 for very little gain.
Now sometime in the future I may decide to let the 100-400 go in favour of some other 400mm option. (and yes as mentioned I know the 100-400 is slightly less than 400mm )