Thanks!
In fact, I was checking this evening and many of our signs finished in some of the last 3D Assets so, yeah it's too hard!
I'm balancing it right now. We also have apparently an issue in the function that compute the minecart speed: the gold weight is influencing in a strange way. We'll surely fix that ^^
Here's a screenshot of the start we have right now : 
Thanks for testing and for your comment! :)