Yeah I had this problem also,
Another problem might be that the "top bit" isnt tall enough and depending on which drag links you use, can ristrict movement. All in all, ive come to think they are a pretty shabbily made part, and not what you would expect when your paying a premium for parts.
Rant over.
I acutally got a mate who was local to me, who put them in the lathe and took them down far enough to get the nyloc on. That or take it to your local engineering shop, tell them abit about what your doing, it will probably interest them, and they might do it for a contribution to the biscuit tin!
HTH Jas