Turnigy 9XR - How to install better buttons
The rubber buttons is the worst aspect of the 9XR. This video shows how to upgrade the buttons.
The small buttons I used for the upgrade are called tactile micro switches and are sold as 4 x 4 x 1.5 mm. The dimensions are however measured from the top. The lower part is actually 5x5mm, so sometimes they are sold as 5 x 5 x 1,5 mm switches. Quite confusing.
You might get away with using slightly higher 2 mm switches, although I have not tested this. I think that you will have problem using wider ones since the 5 mm kind went in with a shoe horn.