Maybe this will help. All wire has some resistance to current flow. The bigger the wire (smaller wire Gauge number), the less resistance it has per foot. For short runs 18 gauge wire should be ok, but for longer runs, 14 gauge is better. In other words the resistance per foot adds up (more with smaller wire). The specs on the barrel connector pigtails say it's good for 5 Amps or so (Z1000 = 5.5 Amps nominal). 18Gauge stranded is rated for about 10 Amps.
The shorter you can make the pigtail wires the better, as they will add less resistance compared to making up the length difference with 14Ga. wire.
