RE: FuntanaS 90-Weak control horn
I did not use the supplied control horns. Instead I used Dubro "giant scale" ones. They are so stiff so It didn't matter which end the ball link goes.
I think guys ARE successfully using the stock horns from what I've read here. I had some high dollar servos in my wings, and didn't want to lose the precision, so I made sure I had a very tight control linkage, and NO twist in the control horns.
I suggest if you do use the supplied horns, that you put the ball link on the servo end as you say, and make sure you use a sturdy servo arm (metal or reinforced pastic). Use just a clevis to the stock horn. That way, the horn will be stronger, and not twist due to an offset ball link.