Which tele-converter for V8 supercar race with 70-200VR2 on D700?

As title suggests, I am attending the V8 supercar race next month, my longest lens that I own is the 70-200f2.8VR2 on my D700. After attending the race last year, this is not long enough for some situations and am thinking of getting a tele-converter. I am leaning towards the 1.7x at the moment since you loose too much optical quality with the 2x anyone used the 1.4 and the 1.7x? is the optical quality loss noticeable on the 1.7x (im not too worried about the loss of a couple of stops of light since I will be slowing the shutter and doing some panning anyway)?

Thanks.