The diameter of the Dubro monster 4-40 link matches the radius of the control horns. When placed between the horns there is a slight amount of range of movement without the cones. The alignment of the servo and control horn should be that there is no lateral movement. When that's aligned right you don't need the cones anyway.
The smaller normal 4-40 links have more lateral range of movement when placed between control horns. For smaller control surfaces that would be fine too.
To to increase the lateral range of movement just use thin washers between the link ball and the horns on both sides. Bolt this together prior to gluing the horn in the surface so the spacing is correct.