In my humble opinion, those (ball sockets) are ok for throttle, but I would rely on standard clevis' and horns for your control surfaces. They are very positive, especially when held closed with a short piece of fuel tubing slipped over the clevis.

The problem with those is that there is no way to hold them in place and they could pull out during flight and that would be that.

Get the standard control horns and clevis's and use those. In other words, I would strongly recommend NOT using ball sockets for the control surfaces at all. I would not trust them for that. As I said, and as you said, throttle is ok, but ailerons, elevator, rudder? Nope. Not a good idea.

DS.