Where to use Window.SetPos()

My initial installer window is the default 497x362, my next screen is 568x490 to contain a larger area for user inputs. I would like to reposition the window higher, on laptops it almost touches the bottom of the screen. It seems there is no where to use Window.SetPos(handle, tPos.X, iNewY) for the installer screen? It doesn't work in the On Preload presumably because the window hasn't been shown yet? Is it possible to re-position a specific screen when it's shown?

Thanks.