Yes, you can purchase the servo wire and extend it yourself. You will need the wire, the ends and the plugs. If you are really good at soldering, then you can just unsolder your wires from the board and solder on your new wires after you have done the ends. I guess you can do the wire first, then put it in the heli and figure out the length and then put the end on it. Either way, it takes a steady hand and good soldering skills.
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Or you can just purchase extensions. The plugs are a little bulky, but it's the fastest way.