Truthfully, I would spend the cash and get proper Servo extension cables. What you have may work, but do you really want to be up in the air when your servo leads disconnect because they were drawing to much current for the extension cables. At the most the cables would be $10. If you are determined to use the cables, hook them up and feel the cables while activating the servos under stress, if the cables show signs of getting warm - you are going to have to get new extension cables. If not, you are probably going to be fine with those cables.

Later,

Ryan