I am no expert on building Ghosts made of bikes, but several problems occur to me. Ghosts are bulky vehicles, which is okay because they are hovering. That is not okay for a wheeled frame. If you use one bike, balancing it will be worst than walking a tight rope and if you use two, you will have a vehicle that will technically work, but because it will only go forward and will not turn at extreme angles, it will be so difficult to drive that it will only be able to be used on wide open planes. Don't let me discourage you, because there may be a way to do it and if there is, the great people of this community will be the ones to know. Just know that it is not going to be a "little project" that costs $50 and can be done over the weekend.