Hard to imagine dimensions Jim without knowing scale you're working in, but width & length shouldn't be a factor in derailments unless your roadbed is so narrow trees or rock outcroppings get in the way. Watch the clearance on curves where car overhangs increase, though usually the short length of log cars minimize the problem.
Great photos in those links, Marc. There are some early 1900's photos of the Rich Brothers logging company in the Green Mountains of Vermont that remind me of the first link you provide.
They climbed the mountain in a series of three switchbacks on 6% grade. Their operating rule was the engine backed up the grade pushing the empty cars for most of the run. Obviously, there was one leg where the scenario reversed and the engine climbed nose forward pulling the cars. Returning with loads, they traveled downhill facing forward with the load behind, again, except on the odd leg. It's that odd leg where runaways occurred and the rules were amended that none of the crew rode anywhere but in the cab of the Shay when on those legs.
This doesn't help Jim with the track layout but he can be formulating work rules while he's grading the foam roadbed.
Wayne