Ballscrew mounting

I'm currently looking at ways of mounting a ballscrew.

The ball screw in question will be 25mm x 5mm.

The problem I have is the ballscrew is going to be held stationary, and I'm struggling to think of a suitable way to secure it.
It's going to be used to power a mill knee, which already has a 20mm hole bored through it (40mm thick casting at that point - machined flat on both sides).

Initial thought was to machine the ball screw to 20mm at the end, with a thread on the end to get a nut on and clamp everything tight. Main problems with this I can see are, the screw could turn as only friction would be holding it, plus this would only leave a 2.5mm (max - it would be less where the screw is cut into it) lip around the end of the ballscrew. Even with a machined collar fitted it may be pushing things a bit.

Due to the shape of the knee, it's going to be hard to alter the hole much. But other thoughts I've had are -

Machine the screw down to say 15mm, which would leave a 5mm lip, which should be enough to drill for one or two dowel pins. Then machine a collar to fit over the 15mm section to locate on the dowel pin(s), then mount dowel pins in the knee casting, which the collar would also locate on. The hole in the knee would obviously be bushed from 20mm down to 15mm, and a nut used to keep everything tight.

Broaching a key into the knee would be the best option, but I don't have access to any broaches.

Other thought was to drill into the casting, at 90degress to the ball screw, and tap it to take a grub screw. The grub screw could then tighten against a flat machined on the ball screw. But I'm not sure about how well this would work.

I'm open to all suggestions/comments/ideas on this one, as I really am struggling to find a suitable solution.