Jake,
Are you sure you're right about this?
From experience it seems easier over the hull. It would put the righting line a foot and a half higher and 2 feet farther out( it's around the hull). I'm certainly no engineer but that's got to change the leverage in relation to the fulcrum.
If this image is what we're talking about ... yeah. No weights have shifted to give it more righting leverage between these two images. You can consider the person and the boat as one fixed system here. It might be easier to hang on with it over the hull - and you might be able to get lower to the water (getting more leverage) if the line is over the hull...but which way the line runs doesn't add anything to the equation with all other things being equal.