I read the items needed to buy at tower for the ucando3d. They list a servo reverser needed, if not using a computer radio. Why can't I just change the position of the linkage on the servo?.

If you just change the linkage at the servo, then the geometry of the pushrod will be different than the other side and you will not get even throws.

You can set up dual elevators without a servo reverser or a reversed servo and without a computer radio, BUT it takes a little work and may not work in all airframes depending on the room available.

You have to move one of the servos higher or lower than the other one by twice the amount of the servo arm length that you are planning on using. Basically, you are keeping the pushrods identical but moving the servos so you can attach the pushrods at opposite sides of the servo.

Confused enough?
Sorry, I don't know how to draw on the computer or a simple drawing would explain it.

In my opinion, just buy a servo reversing Y-harness, some even come with a center-point adjustment. Then use the screw type control horn to fine tune the throw amount as needed.

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.

I think it would work adequately with the arm on the opposite site of the servo body. Isn't there a photo of this setup in the manual?

If it doesn't, then move into the 21st century and get a computer radio. In my (biased) opinion, anyone who is flying 3D should have a computer, if only to play with the mixes and flap/spoilerons.

Leonard

PS Really it should fly fine with the geometry reversed. A computer is just easier and more versatile.