I've got one of those strappy bike racks you hang off the back of the car (it's to take 2 bikes) and find it really fiddly to attach - not to mention all the scratches on the back of the car! Does anyone use the racks that go on the top of the car? Is it hard to get the bikes up (without weight training)? Would you recommend them - or can anyone recommend any other type of rack? Thanks.