I didn't have this much of an issue with this cart, are you doing it with one hand behind your back?
Seriously though, this was pretty straight forward both times I mounted it. My most annoying thing is keeping the nut from turning, but I got around that by putting a small piece of electrical tape over each "slot" touching the nut, then I could hold both sides of the cart with my finger and thumb and get them snug.
Now I'm afraid to hear what you think of the cart, lol
PS: All phono cartridges should have threaded bodies.