I made a quick and unprofessional drawing (I could've used AutoCAD, but I was being lazy) to illustrate that it is in fact possible to do. As you can see, you can make the spine a bit bigger than normal, and connect the supports with it. I think that it is perfectly doable to make the ride stable and safe. It will be a lot more expensive to make, because the forces acting on the track are twice as large as normal, resulting in much more stress on the spine and the supports. So I doubt it'll ever be done. But hey, one can dream right?
Left: side view; right: front view; black = support; grey = track