Muti-hub assembly location

[Kingfisher22]

I had a marine dealer install a Garmin 8612 chartplotter and Reactor 40 autopilot in my boat. They also added a NEMA network with Command link gateway and 3 port hub assembly so I could get engine data to my chartplotter. The engines are twin 2005 Yamaha 150's. Everything works correctly right now for the chartplotter to receive information from the gateway for the engine data. My issue is where everything is mounted and how it is mounted which is in the rear of the boat through an access door under the splashwell. I want to relocate all network items to my cabin area under my helm. There are two reasons for this. First its not a very dry location especially for the Garmin CCU. Second there's such a birds nest of wires back there I couldn't pull my batteries out or service the fuel filters. The way everything is setup now is there are two 9ft pigtail bus wires (6Y8-82521-41-00) that are plugged into my engines on one end and at the other end the two device ports of the hub (6Y8-81920-01-00). In order to move the hub I need a 21ft pigtail bus wire which Yamaha does not make. Can I just extend these wires myself and make a 21ft pigtail bus wire?

[fairdeal]

the way everything is setup now is there are two 9ft pigtail bus wires (6Y8-82521-41-00) ... In order to move the hub I need a 21ft pigtail bus wire which Yamaha does not make. Can I just extend these wires myself and make a 21ft pigtail bus wire?

well, the design recommendation for NMEA 2000 (which is also Command Link)
is that "pigtail wires" - between a device and the bus -
should not exceed "6 meters" - which is 19.685 feet

"21 ft" isn't much more than that - so i suspect there would be no problem...

[Kingfisher22]

Can I leave the original hub in the back of the boat with my 9ft pigtail bus wires connected between the hub and engine and use say a 12ft main bus wire to another hub behind my helm? The gateway would connect to the hub behind the helm. My gateway could then connect to the NEMA backbone behind the helm as well. Power for helm hub off the ignition. Power for the rear hub off the battery. I would rather spend a little extra money on another hub to feel confident I have it right. I have no way of testing all this before I rig it up since the engines are off the boat.