I agree with the guy below me. also, if you look at pictures of the towers, they never really had true corners, they were flattened a bit. Also: if your using MCEdit, take out the ground until you hit the bedrock [at least 2 up from the void]. At that point you can make them taller and add the radio antena when you reach that point. I'm doing the same thing and this helped a lot. Also get rid of the vines, doesn't really fit.

One thing, the North and South Tower look kind of weird because of there Height to width ratio might want to fix that?