Here are two template outlining the different approaches:
Flexible Slider
All axis are flexible. Content is placed in the sliders and pinned to a side. Don't pin the containers for the slider or the slides, though.
FlexibleSlider.hype.zip (15,4 KB)
Auto Height Slider
This version uses proportional scale and changes the height according to the width. Pinning is irrelevant in such a setup, at least in the content. Again, don't pin the containers for the slider or the slides, though.
AutoHeightSlider.hype.zip (16,1 KB)
Hope that helps