Cut the Y-lead approx 1.5 inches from the male plug end, then prepare the bare ends for soldering. Then take a length of servo wire from your LHS, cut to roughly the length you need to extend by, and solder it in place(don't forgot to slide some heatshrink over to tidy the joints up).

OR, extend the leads of two servos in the same manner and plug them into different receiver channels and use mixing to control them(if you have it).

hope that helps.