I'm flying mine with only the servo arm placed on the opposite side of the other servo and had to extend that wire on that servo to. I did this only because is was trying to trouble shoot a glitching problem. I removed the servo reverser and later found that it was not the cause of my glitch and never got around to reinstalling it, the plane doesn't seem to notice that there is any difference in the servo throws, in fact the servos move the same amount up and down until it has moved about 80% then the last 10% one servo will travel a small amount farther, but i found that my plane doesn't fly well with the elivators moving more than 80% anyway, so I'm flying mine with out the reversing Y-harnes and it still flying great. If you aready have a reversing Y-harness then you should use it but if you just dont want to buy one right now you can fly with out it and might not ever notice any difference, I didnt.