It's been a couple of years now but the first Prius I saw for real was parked beside me with two kayaks which I would have estimated to be around that weight (40lbs) sitting on a unique ( to me) airfilled roof rack. I waited until he came back to his car and in the course of my giving him the 3rd. degree he said he regularly travelled from Vancouver Island down the Pacific Northwest coastal highway and return with them up there and said he did not consider the hit on the MPG to be worth considering. The package looked pretty aerodynamic.