A roof rack will add frontal area to the vehicle. Now you will be pushing a big brick through the air. This year I made 10 trips at 700km per trip pulling a trailer. For me , it worked well.

2012 Lotus Evora --------- 95 Mystique MTX - GONE 395,000 Kms --------- Both Zetecs '97 Contour Mtx - stock - GONE