Be careful with the Dual Axis ends that Central sells. My experience with them is that over time serious friction can develop between the actual little ball and the plastic arm. I've neve had such misalignment between the servo and the linkage as to "not" use the MK ball bearing device on the servo end. My opinion is that if you are going to pay for ball bearing stuff then use it all around. If you are going to use the NMP Dual Axis end, then just use metal-pinned Hayes clevis and a Goldberg plastic connector off the 6/32 screw. The Zeque is definitely "worth" ball bearing hardware all around. There is no way (again in my opinion) that the ball-link style connection is going to be the same or last as long as the MK stuff. It took me a long time to convert to BB, but they ARE the way to go. Also, ditto the loose fitting 2.5 mm problem with MK. I use the 3 mm ends now. However, once in a jam I used CA gell and a toothpick to coat the inner wall of the clevis, then threaded in without being able to pull out the titanium end.
Thanks,
Jim W.