New update, for easier/better curves:
As you can see, you no longer have to select the middle part. At the same time, it has an automatic preview feature, for better/easier curves.
That was a great idea, and as you can see, it has been added.
RoCurve is specifically designed for building, as you may know. It allows you to choose how many parts per curve, and calculates the height/width of the curve. I will be providing ruitine updates, as the one described above, to make this more and more relevant/useful 
Enjoy!