At the moment I'm just using a rear bike rack on the car with added ratchet straps to the roof rack. peugeot 206. Sticks out but not much more than ordinary bikes. An old aluminium ladder is my plan for roof top travel. The ladder will sit on the ground and leave one end up on the roof rack. Bike can be rolled up the ramp upright, secured using ratchets or even a modded bike holder. Once attached the ladder can be slid up with the bike on and then secured.