Jim,
Excellent advice from Winston.
1 thing I forgot to add: Any steel structure with a great span is going to bounce or sway a little. It's normal and harmless. It can take numerous stays or extremely large bracing to remove all of the movement, and you get diminishing returns. Just get it "comfortable", and accept a little bit of movement. It will remind everyone they are high up, and make them appreciate your fine structure.
PS: I hope you have pulleys or something smooth to prevent wear on your cables where they run on top of your towers.
