Do something like this for your track power. Pull two wires down the center of the layout connected to the transformer.
Then use 3M splice connectors to cut in the power feeds or drops to connect to the track.
This pic is for one loop. Splice in another set of drops for the inside loop. A 25' roll each of black and red in 14awg for the buss and a 50' roll each of black and red in 16g or 18g for the feeders\drops would do the trick.
