Not trying to tell you how to build it because you are doing an awesome job but a suggestion only, I personally wouldn't put too much thought into the exact lines you want to run because you may become pretty bored with it. Basically I would try to create as many different lines as possible but more of a natural setting instead of a planned setting if that makes sense. A good example would be, "and just an example" , if I wanted a rock bed of some sort on a hill, I would grab a hand full of pebbles, close my eyes, and where they drop is where they will stay. Kind of a natural thing. Toss a hand full of tree with your eyes closed, where ever they land is where I would plant them. I just think it would create more of a thought process when you are actually crawling and not knowing exactly where to drive before you even start.

It's looking awesome. I just hate to see you get bored with it is all. Please don't take this as being a know-it-all, I just thought it would make it a bit more challenging is all.