It might be worth your while to get a bolt-on trailer hitch. With that there is a unit that fits into it that is a rotating post with a cross beam on top of it. You lift one end of the canoe, attach it to the cross beam, then lift the other end of the canoe and rotate it to sit fore and aft on the car top. I don't have the name of the unit here, but can get it to you by this weekend. I have a
16' canoe that weighs 76 pounds. It is now very easy to load and unload it, whereas before it was some kind or wrastle!