I used to think a little extra slack in the governor rope was fine until a safety circuit on a 15-story Otis unit in Philly tripped because of it. | Elevator Mechanics - nhfree.com
Check it with the spring scale like the book says every time. That Philly story is a good warning, but I've seen tight ropes cause just as many problems with binding. You really just need to hit that sweet spot in the middle.
My old foreman in Tampa swore by the quarter trick. He'd have us lift the rope at the midpoint, and if it gave more than a quarter-inch of play, we'd re-tension it. Honestly, it felt a bit superstitious, but his units never had a callback for governor issues in the five years I was there.