Hi Michael,
The problem comes from the fact that in order to set percentage height of the scroller, it needs its parent element to have explicit height set. When you are using percentage height for the scroller it does not actually scroll.
In order to achieve the functionality that you are looking for (using relative height for the scroller) the best approach will be to use CSS flexboxes. You can read more about it here:
http://css-tricks.com/snippets/css/a-guide-to-flexbox/
Or you can also check this example project:
http://www.telerik.com/support/code-library/using-css-flexbox-to-format-content
Regards,
Kiril Nikolov
Telerik
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