Sorry 'bout the long pause... been on holiday. FX or DX? Answer: FX After reading the small print and turning everything off that might distract the camera's "thinking ability" I have managed to get the fabled 100 frame buffer capacity. I'm not at all sure it was worth it mind you, but it was an interesting academic exercise. Nikon declined to answer my direct question about the speed of the bus to the CF card citing "commercial confidentiality".
What I have learned is that there is no point in spending the bucks needed for a 90MB/s CF card. Save your cash, get a slower card with greater capacity instead. I think that if you're that keen to get 100 pix in just over 12 seconds, buy an video or maybe a D4/D800.
The card bus speed is a slightly sore point - I've probably wasted cash because Nikon won't make a recommedation for CF card speeds for fear of somebody (Canon spy?) making a guesstimate on their hardware's performance. I am quite certain that Nikon and Canon reverse engineer each other's products and are therefore fully aware of the facts. The only advantage of a fast card is maybe with having a CF Card reader plugged into a USB 3.0 port. Which I don't have, naturally.
Anyway, I am where I am and now I must get back to sifting through the 1,500 pix taken on a week's holiday. Note to self: Get a life