I think Sulby Straight will be the lowest part of the course, but the coldest part, (i.e. where two strokes were most likely to seize), was Crosby Village.
It was always thought that the prevailing wind, (westerly) blew through the valley from Peel to Douglas. Thus we didn't worry much about Sulby Straight, but getting a two stroke to Greeba Castle was always a bit of a relief.