That's been my experience as well. The problem with trying to run any back lash is that unlike in precise machinery these gearboxes are made of plastic, and pretty soft plastic at that. When you get outside in the summer heat and run a long main, the plastic gets soft and flexes. This causes the lash to become too big and the gears start skipping. Do this a couple of times and bye bye gears. If the gearboxes were all metal and didn't have that extra give you could get away with no backlash.
