Position idlers to get better chain wrap -- a question about good practices.

[Madison]

So, I guess I'm looking for words of advice and consolation as I deal with trying to elegantly tension chain and achieve good wrap around my drive sprockets.

Assume that tensioning is achieved by moving the outer drive wheel and sprocket away from all of the others -- toward the end of the robot. The idler is attached to the frame rail and is fixed in place.

How close can I reasonably put the idler to the gearbox output sprocket (shown floating in space) to achieve increased chain wrap without it being so close that the sprockets are acting as spur gears, too.

Are there any situations that may arise from creating serpentine chain wrap, speaking generally? I've never designed such a complex chain run before; and I realize it's not even that complex.