I designed a curved slope for the Duplo trains.
Now you can build a slope around the corner.
Use the start and end slope of Pjotrx (http://www.thingiverse.com/thing:122268) for starting and ending.
The curved slope is based on 30° pieces and a radius of 260mm (like original.
I haven't tried it yet myself cause I printed just 1 piece yet.
Maybe I add a rack system in the future...