Very nice setup, but what I was referring to is if you were using an extension tube that could be placed between the two towers. A piece of 3" tube cut to size with a couple of ferrules ($6 each, and you could sell the end caps) welded on the ends, additional taps located in the new section. Since you already have forced air, maybe you could increase the flow by reversing the direction on one side. Instead of returning through the same tower, it would be air up one tower, air down the other tower. I fully realize you don't need it, but it sounds like it could be done. Just need 6 or more additional faucets, fittings, kegs, probably a larger CO2 tank, air distribution manifold, and brew time! You already have the hole punch.
Not practical or needed, just possible.
Mainly joking here, be happy with your setup. Now if the evil devil on your shoulder won't shut up, I'll help defray the cost by welding the ferrules.