Do it east to west. Its about 7 miles and downhill. I also recommend doing it at the start. The gradient outweighs any wind considerations, unless you are really into cycling uphill on a busy winding road.
I did it downhill a few years ago and it took me around 20 mins, even though it was before 6 AM there was still a couple of juggernauts zipped past me one after the other which is not a great experience. The less time spent cycling on that road the better I would say, and it would have taken me more than an hour to cycle uphill to the Cluanie and I would have been burst before I even started walking.
You pick up some good speed and a lot of freewheeling on the road down and use only minimum energy.
Of course it means you have extra ascent on the hill but its a good trade off, I reckon.
All the best