Sorry, I meant Height…
I did test a post slider with vertical, scrolling, and if all the posts have the same height it works. But if some posts are higher than other it wont.
Eventually we can add CSS to impose a minimum height for all posts, but that will only work when the browser is as wide as the site. When the browser gets smaller and the text needs to reflow, the posts will increase in size and wont be the same height any more.
The only solution I see if to set a fixed height for the posts and let a vertical scroll bar come up if the posts becomes higher than that fixed height when the browser gets smaller
You would do that by adding the rule below in The SLider Custom CSS box ( at the bottom of the slider options).
.this-slider .slide-content {height:300px !important;overflow-y:auto;}
Adjust the height to be as tall as the tallest posts, so that on a large browser there wont be a scroll bar.