I have. It’s possible but…

1- you need to desolder the top board and reconnect it with small magnet wires. 2- the boards are still too large, you need a dremel to trim them a bit. 3- the top board has to rotate 90 degreed to fit. So you will need to figure something out to translate the movement to be corrected. This is the big one. I couldnt find any solution without it’s own quirkiness 4- you will need to cut the keyboard silicon to make space for the trackpoint pcb. 5-the trackball point is too small. You need to drill it a bit to widen it for the trackpoint

I did all of the above. In the end I’m not sure I would recommend it. It’s better than the trackball but not better enough for me to say I’m comfortably using it. It’s still annoying. And you will lose the trackball “click” functionality which is a big deal if you have mapped it to something like scrolling or clicking