Any binding in the transmission of force to the control surface should be minimized as much as possible. Even then there may be to much, in which case a different approach may be warranted; change to snapper keepers, ball links or clevis). Z-bends are great, when they are correctly made and fit right. I always come up through the servo arm so the point of the Z-bend doesn't rub on the servo case. Any loss of transmitted force should be minimized as much as possible (Aileron twist, servo arm or horn hole to large, etc.) Take a systemic approach to the whole mechinism and try to make it work the best it possibly can. I've seen SPAD type airplanes when aileron input is generated, it actually warped the wing in the opposite direction due to a flappy wings. The plane flew and the owner didn't care, so what the hey!!