Hi,
I should be dumb as I didn’t see how the Handy is locked on your Hands3. Is it Only clamped when pushed inside the cup? It didn’t see any nut or so on the Handy side.
Imo it should fall down at any time if it’s the case. You may add a clamp like on official cup (https://discuss.eroscripts.com/t/handys-handsfree-cup-model-for-3d-printing/106989) to avoid that happen.
Another point to add for convenience would be a wire guide but I don’t know if it’s useful or not.
Enjoy !