Need Help with No Limits Rollercoaster Editor!

I want to make a rollercoaster that will be essentially a big spiral. I have thought of two versions, one where all turns will be exactly the same size (like a screw) and another where each turn will be slightly smaller than the last one (like concentric circles). I have tried hard, but I have two big problems: 1. I cannot make the rails to turn smoothly and 2. I cannot give the rails a constant downwards slope.

I suspect that the main problem is the way I set the vertices. Are there any tips on how to set them and how many to use?