I disliked the placement of the inner buttons, so 3D printed the entire button harness and buttons so I could modify and experiment with paddle placement. I was not expecting it, but the best placement was above the outer buttons. I have included the whole harness and paddles, and also just the paddles.

I have 2 Vader 3 Pro controllers and found the harness fits 1 perfectly and the other not 100%. For the one that doesn't fit 100%, now I know where the paddles should be, I just made 2 small holes, and screwed in just the paddles. This solution doesn't even require you to open the controller. Just don't make the holes too large.

My models are designed for an M2 6 MM, but 5 MM should be fine.