Positioning / Changing size of Slide on fullscreen presentation using VBA?

How can I position and/开发者_运维问答or change the size of the slides on fullscreen slideshow presentation? (While running the slideshow)

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With ActivePresentation.SlideShowSettings.Run()
    .Left = 277
    .Top = 128
    .Width = 380
    .Height = 290
End With

Didn't find a way to avoid "flashing" of first slide.