I model to the edge too, but if I were to have kids running regularly, to stop dives from accidental or careless highspeed rollovers, I'd have a good sized space at the curves bordering the edges, or put a decent guard rail up.
Leaving some space of a few inches away on any portion facing you allows you to lean over to grab this or that while a train is still running. Too close, and the train will likely clip your body as it passes..... unless maybe your real skinny and shirtless 
Reaching over without leaning is very uncomfortable; an unatural postion.
