Cool, thanks! I decided to take upon myself to do it this long Canadian Thanksgiving weekend. I found a perfect spot for the 2-tone horns, facing front, attached to the top crossbar, using a T bracket and each horn's tab, forming a sideways " H ". I will post some photos. An image is worth a thousand words!
I'm planning to add the horns to the stock one, by splitting the wires as follows (blue wires are the Nissan original which I then split 3-way, represented by the orange wiring, to connect all 3 horns):
Does that make sense? By the way, the Hella horns have no markings of positive or negative connectors, so I'm guessing it doesn't matter which polarity I connect in each connector.
Also, what gauge wire can I use? I purchased 14 gauge but it seems too thick to do those 'Y' splitter connectors. Actually even a single piece of stripped 14g won't fit the terminals. Would 18 or 20 gauge be too thin a wire (in terms of amperage) or would it work ok? It's a short run between the horns, maybe 1m to 1.5m (3ft - 5ft).