Unrelated, but if you're exporting SVG graphics from Illustrator, these will need optimising.
Try something like: http://petercollingridge.appspot.com/svg-optimiser
To strip out the junk Illustrator adds to exports.
This should dramatically reduce the size of the SVG - but check that you've not disabled some styling options that might make the illustration look as you intended. For example, I am using rounded endpoints, and tick the 'remove non-essential styles' off, as otherwise those endpoints are removed.
Save the clean SVG file.
I can't give you a full and proper answer on your main question as I'm still learning Hype myself. I typically just tweak the size as needed. If you find the SVG scaling, you might want to set the height and width of the SVG in a text file - and typically match these settings to the same as the viewport numbers. Such as:
<svg xmlns="http://www.w3.org/2000/svg" width="116" height="159" viewBox="0 0 116 159">
Hope this helps you a little.