2 things...
If you are running wireless it shoudn't matter at all.
If you are running wired, then the 2 inner wires of the cable carry the data, the 2 outer wires ISS power. The second station should only connect to the 2 inner wires, color for color (forgive me. The jarheads at Davis Tech support apparently only know colors, they don't know RS-485). Don't try to power the ISS off both consoles.
And a fine point about the wired option...
You should "daisy-chain" the middle console connection as much as possible, not "star" it . That means running the cable from the ISS to the middle console and the cable from the middle console to the second console, with as little distance between the splice from (ISS to console 2) to console 1, as possible.
This is hard to describe in text. Lemme try it this way. If the ISS cable comes into your garage, and the cable to your neighbor comes into the garage, don't splice in another cable there to go to your console. Run both the ISS and second console cables to your console, and make the stub from the junction to your console as short as possible. A few inches, not much more than a foot or 2, especially if you are running at 19,200 baud.
In any case, per the spec, the distance from the ISS to the far console should not exceed 4000 feet.