I'm not really sure what length I ride but I just got a new straight line rope and it makes a huge difference over the $10 Kmart rope. I agree anything slower than 23 and I think the wake gets too washed out and you cant really crank on your cuts.
70 feet at 23-24 mph for more air. At 60 feet, I was landing way out in the flats with major bounce. Landing on the downside of the wake is less painful.