Summary

Great original design. The best available IMHO. I had to improve a few things for our purpose:

Curve + Straight:

1. Raise center piece so action blocks work.
2. Remodel ends so standard Duplo blocks can connect like original Lego design.

Crossing:

1. Remodel ends so standard Duplo blocks can connect like original Lego design.
2. Widen crossings so wide wheels can fit

Notes:
You may notice some small extra notches on the bottom. These are a) for cleaner printing in a continuous line on the base layer and b) for an 'invisible' connector system we use on our tracks.