I don't quite understand the question. Highslide JS expands the image as large as it can, given the size of the viewport (though it won't make the image larger than the JPG's actual dimensions). Are you trying to limit it in some way? If so, why?
You could constrain the expander by employing the
useBox technique seen here:
http://highslide.com/examples/gallery-in-box.html
On the subject of script versions, just stick to
highslide-full.js or
highslide-full.min.js, which is the same thing, only packed tighter. It's not a large script, so there's no point trying to figure out which bits and pieces of the whole thing you actually need.