@DanT Impact will detect touch devices and either remove video slides from the slideshow or display the cover image specified in Touch Device Cover Image settings. By using the stacks visibility settings, you are showing/hiding purely dependent on the screen width (not type) and as such large iPad screens will overlap the width definitions for desktop devices. In your case, for example, using hide for small simply hides the stack for devices/browsers when the width is less that approximately 640px
Thus if using visibility you should use a Foundation visibility stack which cane set to detect touch devices rather than just physical width but this is really a bad idea with Impact…
Just using visibility controls is a bad idea because all this will do is hide the display of a stack but not prevent it loading. This means that for all devices, you are loading both the Impact containing the video and the one containing the slides. This is quite a considerable amount of data (and page load time) when only one or the other is ever seen.
To explain a little more about how the Touch Device Cover Image settings work:
When not enabled (in the main stack settings), Impact will detect touch screen devices and remove any video slides from the slide show.
When enabled, Impact will remove all slides from the slide show and just display the cover image specified.
So, in the context of your setup, this really means that you would need the video as the first slide and the image slides as subsequent slides in one stack. Of course the image slides will also get displayed on non touch devices after the video (set the video child
additional delay setting long enough to allow the video to complete in full). On touch devices you will just get the image slideshow.
If it is absolutely unacceptable to have the image slides after the video on non-touch devices then you are back to using a Foundation visibility in Touch Device mode but, again, I would advise against this as mobile users will be forced to load the entire video which will never be displayed.