I am having the same problem as hexcoder had, in an earlier post: http://wordpress.org/support/topic/long-infographics-pop-up-with-middle-showing-not-top
I tried the solution that you suggested to him--turning on Scaling to Viewport, but that makes our extra-long graphic so narraw as to be illegible. (The text is too small to read.)
You can see it scaled here (the site goes live soon, so if the first link doesn't work, please use the second link):
Ideally, I'd like to have this long graph open in a full-width lightbox, even though the user would have to scroll a lot to read it all.
Other than this one special case, I think your plugin is great, especially because it works on mobile. Keep up the good work.