Applescript, Keynote, Slidesize


I’m trying to make a new slideshow with applescript and change the default slide size. I earlier Keynote versions
set thisSlideshow to make new slideshow with data {theme:chosenTheme, slideSize:{themeWidth, themeHeight}}
seems to have worked, but that doesn’t work in Keynote '09.
Is there any way to control the inspector window of a slideshow via applescript? Thanks for any help.