To set its position, I'm using:
System Every tick
set X to windowWidth/2
Set Y to WindowHeight-100-(spin_btn.Height/2)
The button has its origin set to the center.
The result is that the X & Y values vary widly with the screen size. E.g the longer the window, the more it disappears off below the window. The shorter the window, the more the object launches into outer space. Same with the X value. Its only actually correct when the window size happens to be the same a the window size set in the project.
Here is a 1 sprite capx file:
This is making life very hard...