I know that I'm not the windmill guru on the forum but I whipped up a spread sheet just to check the numbers and see things like total output per tower with the 4+1 cable setup and noticed if you add and extra obstruction on every layer above the very top tower for 4 layers you can set the top windmill at 185 and the top 5 windmills will at most produce 4.98 eu/t.

Imagine the towers look like this as a cross section:

with = Air.

If you add no windmill tower cap the max height of the top tower is 161 for completely safe running. A tower of 16 produces 76.24/t on average. (Calculated at Wind Strength 15)

If you add addition 4 layers of 5 blocks on top of the top layer of wind mills in the same shape as the tower itself the maximum height is 181 (not counting the cap) producing 97.84 eu/t on average for a tower of 16.

But if you add 6 blocks on for each layer above the top tower you can get the top 5 to max at the same virtual height meaning you can bump the tower to 185 for the highest windmill and produce 102.16 eu/t on average for a tower of 16 all running completely safely.

You could possibly make it more effective by trying to balance out the effective height of each windmill but at this point the next one to blow besides the top 5 is the bottom one so it could get messy.

Edit 1: The height of the bottom windmill would be 170 on a tower of 16 if you would like to build this yourself.

Edit 2: Darn spreadsheet didn't remind that its not always a thunderstorm outside, averages are now fixed.