Hmm. I tested 6 pairs of 2.5 mm BB adjusters with the 2.5 mm titanium rod end threads. Dead positive that the thread size is 2.5 mm. These were brand new adjusters with no wear and no previous threading. In each case, after fully threading the adjuster to the max depth, I could separate the the adjuster from the rod end by pulling with my fingers.
Personally,Ive always used the 3mm MK links,with a steel 3mm threaded rod going into it ,and never had a problem----BUT--at the weekend a friend had a nearly-terminal experience with his Evolis when the 2.5mm link tried to come out of the threaded rod at the servo end of the MK thing with a yoke at the aft end,that operates the elevator via two external pushrods.
In his case, there was a sudden gross elevator trim change(Loads of extra down trim).
He managed to get it down safely, and the linkage pulled apart by hand on investigation.
I think I'll stay with two separate elevator servos at the back!