Feel free to copy my idea as long as you give credit where it's due =D. I really don't care for money, just recognition ^_^. I was thinking Zero G corridors to transition between layers. This way you don't have to waste resources making an elevator to go up or down layers. The only transit you need is a Sky Tram on the Zero G inner center layer to get you from one end of the 36 km tube to the other end. A little bit of Zero G a day shouldn't hurt you as long as you're not spending all your time in it. If it's brief moments during the day (a few minutes), it should be fine and not affect your long term health. And with each layer moving in opposite directions, it should be easy to figure out what section you want to climb up to or dive down towards since it's Zero-G environment and you can pull yourself up or hop down.